NYSE: NWN

During the first quarter of 2025, we evaluated the reportable business segments of NW Holdings and concluded that SiEnergy and NWN Water were also reportable business segments. In addition, the NGD segment was renamed to NWN Gas Utility. NW Holdings primarily operates in three reportable business segments, which are NWN Gas Utility, SiEnergy, and NWN Water. NW Natural primarily operates in one reportable business segment, which is NWN Gas Utility. NW Holdings and NW Natural also have investments and business activities not specifically related to the NWN Gas Utility, SiEnergy, and NWN Water segments, which are aggregated and reported as NW Holdings Other.

Our mission is to provide safe, reliable and affordable utility services and renewable energy in a sustainable way to better the lives of the communities we serve. We support our mission by following our core values of service ethic, integrity, safety, caring, and environmental stewardship.

SEGMENT INFORMATION

NWN Gas Utility

NW Natural operates a regulated gas distribution utility servicing customers through approximately 810,000 meters in Oregon and southwest Washington. Approximately 88% of customers are located in Oregon and 12% are located in southwest Washington.

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NW Natural has been allocated an exclusive service territory by the Oregon Public Utility Commission (OPUC) and Washington Utilities and Transportation Commission (WUTC), which includes the major population centers in western Oregon, including the Portland metropolitan area, most of the Willamette Valley, the Coastal area from Astoria to Coos Bay, and portions of Washington along the Columbia River. Major businesses located in NW Natural's service territory include retail, manufacturing, and high-technology industries.

Customers

The NWN Gas Utility business serves residential, commercial, and industrial customers with no individual customer accounting for more than 10% of NW Natural's or NW Holdings' revenues. On an annual basis, residential and commercial customers typically account for approximately 60% of NWN Gas Utility volumes delivered and approximately 91% of NWN Gas Utility margin. Industrial customers largely account for the remaining volumes and margin.

The following table presents summary meter information for the NWN Gas Utility segment as of December 31, 2025:

Number of Meters% of Volumes% of Margin

Residential739,337 37 %66 %

Commercial69,214 23 %25 %

Industrial1,046 40 %5 %

Other(1)
N/AN/A4 %

Total809,597 100 %100 %

(1) NWN Gas Utility margin is also affected by other items, including miscellaneous revenues, gains or losses from NW Natural's gas cost incentive sharing mechanism, other margin adjustments, and other regulated services.

Generally, residential and commercial customers purchase both their natural gas commodity (gas sales) and natural gas delivery services from the NWN Gas Utility business. Industrial and some large commercial customers also purchase the gas commodity either from NW Natural or directly from a third-party gas marketer or supplier. Gas commodity cost is primarily a pass-through cost to customers; therefore, profit margins are not significantly affected by an industrial customer's decision to purchase gas from NW Natural or from third parties. Industrial and large commercial customers may also select between firm and interruptible service levels, with firm services generally providing higher profit margins compared to interruptible services.

To help manage gas supplies, tariffs are designed to provide some certainty regarding industrial and commercial customers' volumes by requiring an annual service election, special rates or possible restrictions for changes between elections.

We estimate natural gas was in approximately 64% of single-family residential homes in NW Natural's service territory in 2025. Customer growth in our region comes mainly from the following sources: single-family housing, both new construction and conversions; multifamily housing new construction; and commercial buildings, both new construction and conversions. Single-family new construction has consistently been our largest source of growth. Continued customer growth is closely tied to consumer preference for natural gas, the comparative price of natural gas to electricity and fuel oil, regulations and building codes permitting the use of natural gas in new construction and conversions, and the economic health of our service territory.

Competitive Conditions

In its service areas, the NWN Gas Utility business has no direct competition from other natural gas distributors. However, it competes with other forms of energy in each customer class. This competition among energy suppliers is based on price, efficiency, reliability, performance, preference, perceptions, market conditions, building codes, technology, federal, state, and local energy policy, and environmental impacts.

For residential and small to mid-size commercial customers, the NWN Gas Utility business competes primarily with providers of electricity, fuel oil, and propane.

In the industrial and large commercial markets, the NWN Gas Utility business competes with all forms of energy, including competition from wholesale natural gas marketers. In addition, large industrial customers could bypass NW Natural's natural gas distribution system by installing their own direct pipeline connection to the interstate pipeline system. NW Natural has designed custom transportation service agreements with several large industrial customers to provide transportation service rates that are competitive with the customer’s costs of installing their own pipeline.

Seasonality of Business

The NWN Gas Utility business is seasonal in nature due to higher gas usage by residential and commercial customers during the cold winter heating months. Other categories of customers experience similar seasonality in their usage but to a lesser extent.

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Regulation and Rates

The NWN Gas Utility business is subject to regulation by the OPUC and WUTC. These regulatory agencies authorize rates and allow recovery mechanisms to provide the opportunity to recover prudently incurred capital and operating costs from customers, while also earning a reasonable return on investment for investors. In addition, the OPUC and WUTC also regulate the system of accounts and issuance of securities by NW Natural.

NW Natural files general rate cases and rate tariff requests periodically with the OPUC and WUTC to establish approved rates, an authorized return on equity (ROE), an overall rate of return (ROR) on rate base, an authorized capital structure, and other revenue/cost deferral and recovery mechanisms.

NW Natural is also regulated by the Federal Energy Regulatory Commission (FERC). Under NW Natural's Mist interstate storage certificate with FERC, NW Natural is required to file either a petition for rate approval or a cost and revenue study every five years to change or justify maintaining the existing rates for the interstate storage service.

For further discussion on our most recent general rate cases, see Part II, Item 7, "Results of Operations—Regulatory Matters—Regulation and Rates."

Gas Supply

NW Natural strives to secure sufficient, reliable supplies of natural gas to meet the needs of customers at the lowest reasonable cost, while maintaining price stability, managing gas purchase costs prudently and supporting our core value of environmental stewardship. This is accomplished through a comprehensive strategy focused on the following items:

•Reliability - ensuring gas resource portfolios are sufficient to satisfy customer requirements under extreme cold weather conditions;

•Diverse Supply - providing diversity of supply sources;

•Diverse Contracts - maintaining a variety of contract durations, types, and counterparties;

•Cost Management and Recovery - employing prudent gas cost management strategies; and

•Environmental Stewardship - striving to reduce the carbon content and environmental impacts of the energy we deliver.

Reliability

To support system reliability, the NWN Gas Utility business has developed a risk-based methodology in which it uses a planning standard to serve the highest firm sales demand day in any year with 99% certainty.

The projected maximum design day firm NWN Gas Utility customer sales is approximately 10 million therms. Of this total, the NWN Gas Utility business is currently capable of meeting approximately 57% of the requirements with gas from storage located within or adjacent to its service territory, while the remaining supply requirements would come from gas purchases under firm gas purchase contracts and recall agreements.

NW Natural segments transportation capacity, which is a natural gas transportation mechanism under which a shipper can leverage its firm pipeline transportation capacity by separating it into multiple segments with alternate delivery routes. The reliability of service on these alternate routes will vary depending on the constraints of the pipeline system. For those segments with acceptable reliability, segmentation provides a shipper with increased flexibility and potential cost savings compared to traditional pipeline service. The NWN Gas Utility business relies on segmentation of firm pipeline transportation capacity that flows from Stanfield, Oregon to various points south of Molalla, Oregon.

We believe gas supplies would be sufficient to meet existing NWN Gas Utility firm customer demand in the event of maximum design day weather conditions.

The following table shows the sources of supply projected to be used to satisfy the design day sales for the 2025-26 winter heating season:

Therms in millionsThermsPercent

Sources of NWN Gas Utility supply:

Firm supply purchases3.4 34 %

Mist underground storage (NWN Gas Utility only)3.4 34 %

Company-owned LNG storage1.8 18 %

Pipeline segmentation capacity0.6 6 %

Off-system storage contract0.5 5 %

Recall agreements0.3 3 %

Total10.0 100 %

The OPUC and WUTC have Integrated Resource Planning (IRP) processes in which utilities define different future scenarios and corresponding resource and compliance strategies in an effort to evaluate supply and demand resource and compliance

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requirements, consider uncertainties in the planning process and the need for flexibility to respond to changes, and establish a plan for providing reliable service while meeting carbon compliance obligations within frameworks that emphasize least cost and risk.

NW Natural generally files a full IRP biennially for Oregon and Washington with the OPUC and the WUTC, respectively, and files updates in Oregon between filings. The OPUC acknowledges NW Natural's action plan, whereas the WUTC provides notice that the IRP has met the requirements of the Washington Administrative Code. OPUC acknowledgment of the IRP does not constitute ratemaking approval of any specific resource acquisition strategy or expenditure. For additional information see Part II, Item 7, "Results of Operations—Regulatory Matters."

Diversity of Supply Sources

NW Natural purchases gas supplies primarily from the Alberta and British Columbia provinces of Canada and multiple receipt points in the U.S. Rocky Mountains to protect against regional supply disruptions and to take advantage of price differentials. For 2025, approximately 60% of gas supply came from Canada, with the balance primarily coming from the U.S. Rocky Mountain region. We believe gas supplies available in the western United States and Canada are adequate to serve NWN Gas Utility customer requirements for the foreseeable future. NW Natural continues to evaluate the long-term supply mix based on projections of gas production and pricing in the U.S. Rocky Mountain region as well as other regions in North America.

NW Natural supplements firm gas supply purchases with gas withdrawals from gas storage facilities, including underground reservoirs and LNG storage facilities. Storage facilities are generally injected with natural gas during the off-peak months in the spring and summer, and the gas is withdrawn for use during peak demand months in the winter.

The following table presents the storage facilities available for NWN Gas Utility business supply:

Maximum Daily Deliverability (therms in millions)Designed Storage

Capacity (Bcf)

Gas Storage Facilities

Owned Facility

Mist, Oregon (Mist Facility)(1)
3.4 13.1

Mist, Oregon (North Mist Facility)(2)
1.3 4.1

Contracted Facility

Jackson Prairie, Washington(3)
0.5 1.1

LNG Facilities

Owned Facilities

Newport, Oregon0.8 1.0

Portland, Oregon1.0 0.6

Total7.0 19.9

(1) The Mist gas storage facility has a total maximum daily deliverability of 5.3 million therms and a total designed storage capacity of about 17.5 Bcf, of which 3.4 million therms of daily deliverability and 13.1 Bcf of storage capacity are reserved for NWN Gas Utility business customers.

(2) The North Mist facility is contracted to exclusively serve Portland General Electric, a local electric utility, and is not used to serve other NWN Gas Utility customers. See "North Mist Gas Storage Facility" below for more information.

(3) The storage facility is located near Chehalis, Washington and is contracted from Northwest Pipeline, a subsidiary of The Williams Companies.

The Mist facility serves NWN Gas Utility segment customers and is also used for non-NWN Gas Utility purposes, primarily for contracts with gas storage customers, including utilities, and third-party marketers. Under regulatory agreements with the OPUC and WUTC, gas storage at Mist can be developed in advance of NWN Gas Utility customer needs but is subject to recall when needed to serve such customers as their demand increases. When storage capacity is recalled for NWN Gas Utility purposes it becomes part of the NWN Gas Utility segment. As of May 1, 2025, 0.2 million therms per day of deliverability and 0.3 Bcf of associated non-utility Mist gas storage capacity was recalled to serve core customers. Customer rate increases related to this recall began for Oregon customers on October 31, 2025, and November 1, 2025 for Washington customers..

Diverse Contract Durations and Types

NW Natural has a diverse portfolio of short-, medium-, and long-term firm gas supply contracts and a variety of contract types including firm and interruptible supplies as well as supplemental supplies from gas storage facilities.

The majority of our gas supply contracts include year-round, winter-only, summer-only, and monthly baseload supplies, and daily spot purchases. We also maintain options to call on additional daily supplies during the winter heating season.

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During 2025, a total of 784 million therms were purchased under contracts with durations as follows:

Contract Duration (primary term)Percent of Purchases

Long-term (one year or longer)40 %

Short-term (more than one month, less than one year)41

Spot (one month or less)19

Total100 %

During 2025, there was no individual supplier that provided 10% or more of the NWN Gas Utility business gas supply requirements.

Gas Cost Management

The cost of gas sold to NWN Gas Utility customers primarily consists of the following items, which are included in annual Purchased Gas Adjustment (PGA) rates: gas purchases from suppliers; charges from pipeline companies to transport gas to our distribution system; gas storage costs; gas reserves costs; gas commodity derivative contracts; and renewable natural gas and its attributes, including renewable thermal certificates. Costs to comply with Washington's Climate Commitment Act (CCA) are included in the cost of gas for Washington customers. We expect costs to comply with Oregon's Climate Protection Program (CPP) and any similar program that may be enacted in our service territory will also be included in the cost of gas.

The NWN Gas Utility business employs a number of strategies to mitigate the cost of gas sold to customers. The primary strategies for managing gas commodity price risk include:

•negotiating fixed prices directly with gas suppliers;

•negotiating financial derivative contracts that: (1) effectively convert floating index prices in physical gas supply contracts to fixed prices (referred to as commodity price swaps); or (2) effectively set a ceiling or floor price, or both, on floating index priced physical supply contracts (referred to as commodity price options such as calls, puts, and collars); and

•buying physical gas supplies at a set price and injecting the gas into storage for price stability and to minimize pipeline capacity demand costs.

NW Natural also contracts with an independent energy marketing company to capture opportunities regarding storage and pipeline capacity when those assets are not serving the needs of NWN Gas Utility business customers. Asset management activities provide opportunities for cost of gas savings for customers and incremental revenues for NW Natural through regulatory incentive-sharing mechanisms. These activities, net of the amount shared, are included in other for segment reporting purposes.

Gas Cost Recovery

Mechanisms for gas cost recovery are designed to be fair and reasonable, with an appropriate balance between the interests of customers and NW Natural. In general, natural gas distribution rates are designed to recover the costs of, but not to earn a return on, the gas commodity sold. Risks associated with gas cost recovery are minimized by resetting customer rates annually through the PGA and aligning customer and shareholder interests through the use of sharing, weather normalization, and conservation mechanisms in Oregon. See Part II, Item 7, "Results of Operations—Regulatory Matters".

Environmental Stewardship

Part of our gas supply strategy is working to reduce the carbon content and the environmental impacts of the energy we deliver. To that end, NW Natural developed and implemented an emissions screening tool that uses Environmental Protection Agency (EPA) data to calculate the relative emissions intensity of gas producer operations and prioritize purchases from lower emitting producers. In 2019, we implemented this emissions intensity screening tool alongside other purchasing criteria such as price, credit worthiness and geographic diversity. We view this as a cost-effective way to reduce carbon emissions associated with our natural gas supply.

NW Natural is focused on taking steps to lower emissions on behalf of customers by purchasing environmental attributes that are generated by the production of renewable natural gas (RNG). Under Oregon Senate Bill 98, NW Natural can purchase RNG or invest in RNG facilities, which generate these environmental attributes known as Renewable Thermal Certificates (RTCs). In 2019, the Washington State legislature also passed a bill supporting RNG procurement, House Bill 1257. The RTCs work like renewable energy certificates, or RECs, used in electricity markets. RTCs are verified and certified by the Midwest Renewable Energy Tracking System (M-RETS). The M-RETS Renewable Thermal Tracking System issues one RTC for every dekatherm of RNG injected into the gas system. NW Natural enters into contracts for the purchase of RNG and RTCs either through periodic request for proposals or through formal offerings or informal requests. See Part II, Item 7, "Results of Operations—Regulatory Matters".

In addition to purchases of RNG, NW Natural has piloted a hydrogen blend in pipelines serving its Sherwood Operations and Training Center. NW Natural has successfully tested a blend of up to 20% hydrogen. The tests met the safety protocols established by PHMSA Part 192.

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NW Natural is subject to the requirements of the Washington CCA cap-and-invest program, and is also subject to Oregon's CPP. NW Natural has modeled pathways to compliance with the CCA and CPP in its most recent IRP. While costs associated with each possible compliance pathway differ, we are recovering costs associated with compliance with the current CCA and CPP in rates.

Transportation of Gas Supplies

NW Natural's gas distribution system is reliant on a single, bi-directional interstate transmission pipeline to bring gas supplies into the natural gas distribution system. Although dependent on a single pipeline, the pipeline’s gas flows into the Portland metropolitan market from two directions: (1) the north, which brings supplies from the British Columbia and Alberta supply basins; and (2) the east, which brings supplies from Alberta as well as the U.S. Rocky Mountain supply basins.

NW Natural incurs monthly demand charges related to firm pipeline transportation contracts. These contracts have expiration dates ranging from 2026 to 2061. The largest pipeline agreements are with Northwest Pipeline. NW Natural actively works with Northwest Pipeline and others to renew contracts in advance of expiration to ensure gas transportation capacity is sufficient to meet customer needs.

Rates for interstate pipeline transportation services are established by FERC within the U.S. and by Canadian authorities for services on Canadian pipelines.

Gas Distribution

Safety and the protection of employees, customers, and our communities are, and will remain, top priorities. NW Natural constructs, operates, and maintains its pipeline distribution system and storage operations with the goal of ensuring natural gas is delivered and stored safely, reliably, and efficiently.

NW Natural has one of the most modern distribution systems in the country with no identified cast iron pipe or bare steel main. Since the 1980s, NW Natural has taken a proactive approach to replacement programs and partnered with the OPUC and WUTC on progressive regulation to further safety and reliability efforts for the distribution system. In the past, NW Natural had a cost recovery program in Oregon that encompassed programs for cast iron replacement, bare steel replacement, transmission integrity management, and distribution integrity management programs as appropriate.

Natural gas distribution businesses are likely to be subject to greater federal and state regulation in the future. Additional operating and safety regulations from the U.S. Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) are currently under development. In January 2025, PHMSA released the final rulemaking: Gas Pipeline Leak Detection and Repair. The rulemaking includes congressional mandates from the PIPES (Protecting our Infrastructure of Pipelines and Enhancing Safety) Act of 2020 to reduce methane emissions from new and existing gas transmission, distribution, gathering, underground storage, and LNG facilities. The unpublished rulemaking was placed on a regulatory freeze by the new presidential administration and is expected to undergo additional review and amendment. In September 2023, PHMSA issued a notice of proposed rulemaking: Safety of Gas Distribution Pipelines and Other Pipeline Safety Initiatives. The proposed rulemaking requires operators to update distribution integrity management programs, emergency response plans, operations and maintenance manuals, and other safety practices. In May 2025, PHMSA published an Advance Notice of Proposed Rulemaking (ANPRM) on Repair Criteria for Hazardous Liquid and Gas Transmission Pipelines and proposed amendments to Liquefied Natural Gas (LNG) facility safety standards. NW Natural does not foresee a significant impact of these rulemakings on our business given the modern materials used in our system. However, we continue to monitor developments closely, particularly regarding methane reduction requirements, repair criteria, and LNG facility standards, to ensure compliance and maintain safe and reliable operations.

Mist Gas Storage Operations

The Mist gas storage facility began operations in 1989 and has been expanded twice previously. The first expansion in 2001 (Interstate Storage Facility) and again in 2019 (North Mist Gas Storage Facility). The Mist facility benefits from limited competition as there are few storage facilities in the Pacific Northwest region. Therefore, NW Natural not only serves its core natural gas utility customers, it also has the ability to acquire high-value, multi-year contracts for capacity that is not dedicated to its core customers today. Currently, our Mist Storage Operations has a total of 21.6 Bcf with the following customers:

•Gas Utility Storage: 13.1 Bcf used to provide gas storage for the NWN Gas Utility business and included in the NWN Gas Utility segment.

•Interstate Storage: 4.4 Bcf serving Interstate customers and contracted with other utilities, and third-party marketers with these results reported in other.

•North Mist Storage: 4.1 Bcf contracted solely to Portland General Electric to fuel its gas-fired electric power generation facilities and included in the NWN Gas Utility segment.

Gas Utility Storage

The overall Gas Utility and Interstate Storage facility with 17.5 Bcf of storage consists of seven depleted natural gas reservoirs, 21 injection and withdrawal wells, a compressor station, injection and withdrawal lines, and other related facilities. Of the 17.5 Bcf storage facility, 13.1 Bcf serves NWN Gas Utility customers. Under regulatory agreements with the OPUC and WUTC, gas storage at Mist can be developed in advance of NWN Gas Utility customer needs but is subject to recall when needed to serve

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such customers as their demand increases. When storage capacity is recalled for NWN Gas Utility purposes it becomes part of the NWN Gas Utility segment. As of May 1, 2025, 0.2 million therms per day of deliverability and 0.3 Bcf of associated non-utility Mist gas storage capacity was recalled to serve core customers. Customer rate increases related to this recall began for Oregon customers on October 31, 2025, and November 1, 2025 for Washington customers.

Interstate Storage Facility

Of the 17.5 Bcf facility, 4.4 Bcf serves Interstate customers. The interstate storage services are offered under a limited jurisdiction blanket certificate issued by FERC. Under NW Natural's interstate storage certificate with FERC, NW Natural is required to file either a petition for rate approval or a cost and revenue study every five years to change or justify maintaining the existing rates for the interstate storage service. Intrastate firm storage services in Oregon are offered under an OPUC-approved rate schedule as an optional service to certain eligible customers.

North Mist Gas Storage Facility

The North Mist gas storage facility began operations in 2019. The North Mist facility provides long-term, no-notice underground gas storage service and is dedicated solely to Portland General Electric (PGE) under a 30-year contract with options to extend up to an additional 50 years upon mutual agreement of the parties. PGE uses the facility to fuel its gas-fired electric power generation facilities.

North Mist includes a reservoir providing 4.1 Bcf of available storage, a compressor station with a contractual capacity of 120,000 dekatherms of gas deliverability per day, no-notice service that can be drawn on rapidly, and a 13-mile pipeline to connect to PGE's Port Westward gas plants in Clatskanie, Oregon.

The facility is included in rate base under an established tariff schedule with revenues recognized consistent with the schedule. Billing rates are updated annually to the forecasted depreciable asset level and forecasted operating expenses.

Mist Additional Expansion Potential

Mist has a number of depleted reservoirs that have not been developed into storage at this time. As a result, NW Natural has additional expansion opportunities in the Mist storage field. To explore our opportunities, we applied for an Energy Facility Siting Council (EFSC) permit and received approval in January 2025. The permit provides flexibility for potential upgrades and expansions. In February 2026, we announced a planned 4-5 Bcf expansion at our North Mist gas storage facility. This expansion is subject to certain conditions including the customers' final approval of project costs and notice to proceed. Storage expansion projects take multiple years to develop and put into service. We have not included any storage expansion costs within our planned capital expenditures outlined in “Financial Conditions – Investing Activities”. Any future expansion would be based on market demand, cost effectiveness, available financing, receipt of future permits, and other rights.

SiEnergy

SiEnergy owns regulated gas distribution utilities servicing residential and commercial customers through approximately 90,000 meters, primarily in the Dallas/Fort Worth, Houston, and Austin, Texas metro and surrounding areas. SiEnergy also serves transmission customers in Dallas/Fort Worth and Austin, Texas metro areas.

Customers within the areas serviced by SiEnergy include residential and commercial. No individual customer accounts for more than 10% of SiEnergy’s revenues. During 2025, residential and commercial customers accounted for 88% of SiEnergy’s volumes and 93% of margin. Transmission customers represented the remaining volumes and operating revenues.

Development efforts and market demand

Customer growth primarily comes from the following sources: single-family housing, primarily from new construction; multifamily housing new construction; and commercial buildings. Single-family new construction has consistently been SiEnergy's largest source of growth. Continued customer growth is closely tied to significant growth and development in the new construction market.

Competitive conditions

In its service areas, SiEnergy encounters competition based on preference for natural gas, compared with other energy alternatives and their comparative prices, as well as competition from other natural gas utilities. SiEnergy competes primarily to supply energy for space and water heating, cooking and clothes drying. Significant energy usage competition occurs between natural gas and electricity in the residential and small commercial markets. In Texas, the absence of defined service territories increases competitive intensity, as multiple gas utilities may compete directly to obtain business from developers, builders, and end-use customers. Competition among energy suppliers is based on price, efficiency, reliability, performance, preference, perception, market conditions, technology, federal, state, and local energy policy, and environmental impacts.

Developers and builders typically make the decision on the type of equipment, and therefore the energy source, at initial installation, generally locking in the chosen energy source for the life of the community. Changes in the competitive position of natural gas relative to electricity and other energy alternatives have the potential to cause a decline in consumption of natural gas or in the number of natural gas customers. In Texas, SiEnergy is also subject to competition from other local distribution companies who compete directly for gas sales to end users.

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For residential, commercial, and transmission customers, SiEnergy primarily competes with providers of electricity and other fuel sources.

Seasonality of Business

SiEnergy's natural gas sales are seasonal in nature due to higher gas usage by residential and commercial customers during the cold winter heating months (November through March). Other categories of customers experience less seasonality in their usage.

Regulation and rates

Under Texas' regulatory paradigm, original jurisdiction over natural gas distribution rates is shared between the Railroad Commission of Texas (RRC) and the municipalities where the utility provides service. The RRC has exclusive original jurisdiction over natural gas utility rates in areas outside of municipalities. A municipality has original jurisdiction over the rates, operations and services provided by any gas utility distributing natural gas within city or town limits, unless it has surrendered its original jurisdiction to the RRC. However, any municipal rate decision can be appealed to the RRC, which will conduct its own review, including compiling a new evidentiary record. SiEnergy's last general rate case was settled in 2023 with new rates effective in September 2023.

In certain territories, between rate cases, SiEnergy can adjust rates through annual filings pursuant to the Gas Reliability Infrastructure Program (GRIP) statute. In the most recent rate case in 2023, where the territories were not eligible to file GRIP, the Commission found it reasonable to establish uniform rates for SiEnergy customers based on a system-wide cost of service. In 2025, SiEnergy made annual GRIP filings for the incorporated cities and unincorporated areas in its eligible service area. SiEnergy has suspended changing rates through GRIP until the next rate case.

SiEnergy does not currently have any open or ongoing general rate cases and is continuously evaluating the need for future general rate cases.

In June 2025, Texas House Bill 4384 was signed into law, allowing gas utilities in Texas to defer, and later recover, specific costs related to property, plant and equipment placed in service, but not yet reflected in base rates, including depreciation, ad valorem taxes, and carrying cost. The RRC is required to adopt rules to implement the new law within 270 days of the effective date. SiEnergy applied the new provisions to property, plant and equipment placed in service but not yet reflected in rates in 2025. The impact was not material for 2025.

For further discussion on our most recent general rate case, see Part II, Item 7, “Results of Operations – Regulatory Matters – Regulation and Rates”.

Gas Supply

SiEnergy sources its gas supply from producers and processors across Texas, the nation’s largest natural gas‑producing state, through contracts with a variety of natural gas marketers. SiEnergy maintains a diversified set of pipeline interconnects with both intrastate and interstate systems statewide. Alongside SiEnergy's supply agreements, the Railroad Commission of Texas’s Critical Infrastructure Division has standards for the natural gas supply chain during severe weather or emergencies to help ensure reliable upstream gas production and delivery.

Curtailment policies in SiEnergy's tariff prioritize household and critical facility service by allowing the reduction of non-critical industrial and commercial use if needed. A secondary source of supply during an extreme weather event is gas maintained in storage. SiEnergy holds contracts with CNG and LNG virtual pipeline providers for use during force majeure events and extreme weather. With sufficient pipeline reservations and supply contracts in place, SiEnergy does not anticipate issues meeting customer demand.

SiEnergy purchased 2.95 Bcf and 2.26 Bcf of natural gas supply in 2025 and 2024, respectively. These purchases were procured via seven evergreen contracts that span various pipelines and consist of varying terms from a diverse group of suppliers. Natural gas is acquired from natural gas processors, marketers and producers, which mitigates the impact of physical interruptions, natural disasters and unforeseen events on gas supply needed to meet customer demands. In managing natural gas supply portfolios, SiEnergy utilizes a combination of stored natural gas and seasonal reservation changes to reduce customer price volatility.

During 2025, there were five individual suppliers that provided 10% or more of SiEnergy gas supply requirements.

NWN Water Utility

NWN Water provides water and wastewater utility services (utility services) through its wholly-owned subsidiaries to approximately 81,000 water and wastewater connections to customers in Oregon, Washington, Idaho, Texas, and Arizona. NWN Water also provides operations, maintenance and management services (contract services) to water and wastewater system owners serving approximately 38,000 connections in Oregon, Washington, and California.

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During 2025, utility services accounted for 87% of NWN Water's operating revenues. Public Utility Commission regulated utilities accounted for 64% of operating revenues, and an additional 23% of operating revenues come from water and wastewater utility services where NWN Water is the sole provider. Contract services account for the remainder. No individual customer accounts for more than 10% of NWN Water's revenue.

Customers in the areas serviced by NWN Water utility service and contract service businesses include residential, commercial, irrigation, and fire protection users. Residential and commercial customers make up the majority of the utility services business.

Development efforts and market demand

Historically, NWN Water has grown primarily through acquisitions of existing businesses. While we may pursue new strategic acquisitions or joint ventures in the future, our current strategy emphasizes organic growth, including expanding our existing water and wastewater service areas (including through exclusive agreements for new developments) and expanding our contract services model.

Outside of growth through acquisitions, customer growth primarily comes from the following sources: single-family housing, primarily from new construction; multifamily housing new construction; and commercial building new construction. Single-family and multi-family housing new construction has consistently been our largest source of non-acquisition related growth.

Competitive conditions

NWN Water regulated utilities have no direct competition from other water providers because they operate in service areas pursuant to franchises, charters, certificates of public convenience and necessity or similar authorizations issued by state utility commissions. Our utilities that are not regulated by state utility commissions are regulated by other state and local agencies (such as a department of environmental quality), which, in some cases, provide us exclusive service areas and, in many cases, create a barrier to market entry. NWN Water faces competition when purchasing water rights, pursuing exclusive service rights for new developments, and executing strategic acquisitions. Competition in contract services comes primarily from other contract service companies that provide the same type of operations, maintenance and management services.

Sources

The NWN Water utility services business generally own the physical assets used to source, store, pump, treat and deliver water to its customers and collect, treat, and dispose of wastewater from its customers. Generally, water utility operations obtain water supply from wells or surface water sources. Our water operations are primarily self-supplied. An immaterial portion of our water supply is purchased from other water suppliers.

We continuously monitor demands against the capacity of our supply and believe water supply is sufficient to meet the requirements of our customers. For areas that require water rights to acquire water supply, we believe that we have sufficient water rights or ability to purchase more to meet our demands.

Drought, governmental restrictions, overuse of sources of water, the protection of threatened species or habitats, contamination or other factors may limit the availability of ground and surface water. If any of the foregoing occur, our revenues and net income may be adversely affected. There have not been any supply restrictions that have materially impacted our business in the last year.

We believe our wastewater treatment facilities are generally sufficient to meet the requirements of our customers. Most of our wastewater is treated at our own facilities. We obtain and maintain appropriate permitting for our wastewater treatment facilities.

Regulation and Rates

The wholly-owned regulated water businesses of NWN Water are subject to regulation by the utility commissions in the states in which they are located, which currently includes Oregon, Washington, Arizona, Idaho, and Texas. In addition, NWN Water includes wholly-owned unregulated wastewater businesses in Oregon, Washington, and Idaho.

For further discussion on our most recent general rate cases, see Part II, Item 7, “Results of Operations – Regulatory Matters – Regulation and Rates”.

Water and wastewater operations are subject to extensive federal, state, and local regulations governing environmental protection, health and safety, water quality, and the collection, treatment, discharge, recycling, and disposal of wastewater. Key federal laws include the Safe Drinking Water Act, the Reduction of Lead in Drinking Water Act, and the Clean Water Act, along with various state and local requirements that may be more stringent. NWN Water is also regulated in the storage of hazardous materials, the management and disposal of hazardous and solid waste, and discharges to air and water. In addition, state public utility commissions set standards and conditions for the water and wastewater services the Company provides.

Seasonality

Water usage per customer varies throughout the year based largely on local weather patterns. Demand typically rises from May to September, when customers engage in greater irrigation usage. As a result, the largest share of operating revenues typically occur during the second and third quarters of the year. Extended dry conditions during these periods increase consumption, and warmer temperatures contribute to higher water usage. In certain circumstances, prolonged dry weather in our services areas

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could prompt governmental agencies to issue drought advisories or implement water-use restrictions, which would reduce customer usage during those periods. Our wastewater and services businesses do not experience significant seasonality.

OTHER

Certain businesses and activities of NW Holdings and NW Natural are aggregated and reported as other for segment reporting purposes.

NW Natural

The following businesses and activities are aggregated and reported as other under NW Natural, a wholly-owned subsidiary of NW Holdings:

•Interstate storage;

•natural gas asset management activities; and

•appliance retail center operations.

See "Interstate Storage Facility" section above in our descriptions of Mist Gas Storage Operations. The financial results of this business are included in NW Natural Other.

Asset Management Activities

NW Natural contracts with an independent energy marketing company to provide asset management services, primarily through the use of natural gas commodity exchange agreements and natural gas pipeline capacity release transactions. The results of these activities are included in other, except for the asset management revenues allocated to NWN Gas Utility business customers pursuant to regulatory agreements, which are reported in the NWN Gas Utility segment.

NW Holdings

These include the following businesses and activities aggregated under NW Holdings:

•NW Natural Renewables Holdings, LLC and its non-regulated renewable natural gas activities;

•a minority interest in the Kelso-Beaver Pipeline held by NW Holdings' wholly-owned subsidiary NNG Financial Corporation (NNG Financial); and

•holding company and corporate activities, including business development activities, as well as adjustments made in consolidation.

NWN Renewables

NWN Renewables is an unregulated subsidiary of NW Natural Holdings established to pursue unregulated RNG activities. Ohio Renewables, a subsidiary of NWN Renewables, has agreements with a subsidiary of EDL, a global producer of sustainable distributed energy, to secure RNG supply from two EDL facilities that convert landfill waste gases to RNG (EDL Facilities). Ohio Renewables paid $51.4 million to the EDL subsidiaries in 2024 on the completion of the production facilities. RNG production from the facilities began in 2024.

Alongside these development agreements, Ohio Renewables and the subsidiary of EDL executed agreements for Ohio Renewables to purchase up to an annual specified amount of RNG produced by the EDL Facilities over a 20-year period at a contractually specified price. In December 2025, Ohio Renewables contracted to purchase additional RNG volumes produced by the EDL Facilities from a separate investment-grade counterparty for up to certain specified amounts in each of the calendar years from 2026 to 2036. Contracted purchase volumes are based on the EDL Facilities' production volumes set at contractually specified prices. Ohio Renewables has contracted to sell the supply obtained from the EDL Facilities at primarily fixed prices to investment grade counterparties.

Ohio Renewables has contracted to sell some of the RNG produced by the EDL Facilities up to certain specified volumes in each of the calendar years 2024 through 2026 to an investment-grade counterparty. We currently estimate RNG volumes to be sold pursuant to this agreement to be approximately 2,370,000 MMbtu over the life of the agreement, provided that such amounts of RNG are produced by the EDL Facilities during that period.

Ohio Renewables additionally has contracted to sell a fixed-volume of RNG under a long-term agreement with an investment-grade utility beginning in 2025 and extending through 2044. Amounts to be delivered under this agreement are estimated to be 375,000 MMbtu in 2026, 1,950,000 MMbtu annually in 2027 through 2030, and 2,325,000 MMbtu annually in years 2031 through 2034 and 2,775,000 MMbtu annually in years 2035 through 2043 and 1,513,770 MMbtu in 2044.Under the current contract, if less than 75% of the contracted volumes of RNG are delivered annually, Ohio Renewables is obligated to pay the per MMbtu price for volumes between the amount delivered and 75% of the contracted volumes on an annual basis.

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ENVIRONMENTAL MATTERS

Properties and Facilities

NW Natural owns, or previously owned, properties and facilities that are currently being investigated that may require environmental remediation and are subject to federal, state, and local laws and regulations related to environmental matters. These laws and regulations may require expenditures over a long time frame to address certain environmental impacts. Estimates of liabilities for environmental costs are difficult to determine with precision because of the various factors that can affect their ultimate disposition. These factors include, but are not limited to, the following:

•the complexity of the site;

•changes in environmental laws and regulations at the federal, state, and local levels;

•the number of regulatory agencies or other parties involved;

•new technology that renders previous technology obsolete, or experience with existing technology that proves ineffective;

•the level of remediation required;

•variations between the estimated and actual period of time that must be dedicated to respond to an environmentally-contaminated site; and

•the application of environmental laws that impose joint and several liabilities on all potentially responsible parties.

NW Natural has received recovery of a portion of such environmental costs through insurance proceeds, seeks the remainder of such costs through customer rates, and believes recovery of these costs is probable. In both Oregon and Washington, NW Natural has mechanisms to recover expenses. Oregon recoveries are subject to an earnings test. See Part II, Item 7, "Results of Operations—Regulatory Matters—Rate Mechanisms—Environmental Cost Deferral and Recovery", and Note 2 and Note 17 to the Consolidated Financial Statements in Item 8 of this report for more information.

Greenhouse Gas Matters

For information concerning greenhouse gas matters, see Part II, Item 7, “Results of Operations—Environmental Regulation and Legislation Matters.”

HUMAN CAPITAL

Our core values of integrity, safety, caring, service ethic, and environmental stewardship guide how we engage with customers, stakeholders, shareholders, and communities. We actively work to foster these values in our employee culture and to nurture an inclusive and equitable environment that provides opportunities, prioritizes health and safety, encourages respect and trust, and supports growth and learning. We aim to recruit and retain employees who share our core values and reflect our communities.

Employees

At December 31, 2025, our workforce consisted of the following:

NW Natural:

Unionized employees(1)
638

Non-unionized employees660

Total NW Natural1,298

Other Entities:

SiEnergy employees134

Water and wastewater company employees184

Other3

Total other entities321

Total Employees1,619

(1) Members of the Office and Professional Employees International Union (OPEIU) Local No. 11, AFL-CIO.

NW Natural's labor agreement with members of OPEIU covers wages, benefits, and working conditions. In May 2024, NW Natural's unionized employees ratified a collective bargaining agreement that is in effect June 1, 2024 through May 31, 2028, and is effective thereafter from year to year unless either party serves notice of its intent to negotiate modifications to the collective bargaining agreement. The terms of the collective bargaining agreement include the following items: a 6% wage increase effective June 1, 2024 and scheduled wage increases effective December 1 in the first year and each subsequent year of 4%; a 401(k) contribution of 4% for employees hired after our pension plan was closed on December 31, 2009; and a 401(k) match of 50% of the first 8% of savings. During calendar year 2025, NW Natural did not incur any work stoppages (strikes or lockouts), and therefore, experienced zero idle days for the year.

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Certain subsidiaries may receive services from employees of other subsidiaries. Those services are generally charged to the entity receiving those services. When such services involve regulated entities, those entities receiving services are generally charged rates pursuant to shared services agreements that are filed with the applicable state regulatory commission, as applicable.

Safety

Safety is one of our greatest responsibilities to employees. In managing the business, we strive to foster a safety culture focused on prevention, open communication, collaboration, and a strong service and safety ethic. We believe employee safety is critical to our success. A portion of executives’ compensation is tied to achieving our identified safety metrics, and our Board of Directors regularly reviews company safety metrics and receives reports on matters of health and safety. NW Natural and NW Holdings' subsidiaries health and safety policies and procedures are designed to comply with applicable regulations, but we also work to go beyond compliance by striving to incorporate information we learn from benchmarking, peer reviews, and industry best practices.

As part of our commitment to employee health and safety, we maintain regular training programs, emergency preparedness procedures, and training and procedures to identify hazards and handle high-risk emergency situations. Employees complete classroom instruction and hands-on, scenario-based training at our training town facility in Oregon that allows employees to experience realistic situations in a controlled environment. We also host natural gas safety training events for first responders, which are designed to prepare those first responders and NW Natural field employees to deliver an integrated, seamless response in the event of an emergency that involves or affects the natural gas system. We also have a learning management system that provides virtual training options and more efficiency and flexibility in how we train.

Employee Benefits and Support

To attract employees and meet the needs of our workforce, NW Natural and NW Holdings' subsidiaries strive to offer competitive compensation and benefits packages to employees. The benefits package options vary depending on type of employee and date of hire. NW Holdings and NW Natural continuously look for ways to support employees’ work-life balance and well-being and this is reflected in physical, mental and financial wellness programs to meet the needs of our employees and help them care for their families. Benefits available to employees during 2025 included, among others: healthcare and other insurance coverages, wellness resources, retirement and savings plans, paid time off programs, and flexible and hybrid work schedules, where possible, employee resource groups, and culture and community-focused resources and opportunities, and employee recognition programs and discounts.

Talent Attraction and Development

In order to implement our business strategy and serve our customers, we depend upon our continuing ability to attract and retain talented professionals and a technically skilled workforce, and being able to transfer the knowledge and expertise of our workforce to new and increasingly diverse employees as our older workforce retires. A significant portion of our workforce is currently eligible or will reach retirement eligibility within the next five years, and therefore, we are focused on efforts to attract, train, and retain appropriately qualified and skilled workers to prevent loss of institutional knowledge or skills gaps.

NW Natural and NW Holdings subsidiaries seek to provide its employees with growth and development opportunities through programs designed to build skills and relationships. These programs currently include: (i) a culturally relevant mentoring program that creates opportunities for career growth by building relationships; (ii) a tuition assistance program for qualified educational pursuits; (iii) an internal class that provides participants with a big-picture understanding of the industry and company operations, equipping them to see how they contribute to NW Natural and NW Holdings' subsidiaries success and identify opportunities for career growth; (iv) internal and external continuing educational courses relevant to areas of expertise; and (v) ongoing management and leadership training programs.

We regularly monitor employee engagement and satisfaction through a variety of tools, including our annual engagement survey that is designed to enable company leaders to gather valuable feedback and guidance from employees.

Creating a diverse and inclusive culture and workforce that reflects and supports the communities we serve contributes to long-term success. Our efforts in recruiting, promoting, and retaining talent with a wide range of backgrounds, building inclusive teams, and creating a culture that embraces differences are elements of our workforce strategy.

INFORMATION ABOUT OUR EXECUTIVE OFFICERS

For information concerning executive officers, see Part III, Item 10.

AVAILABLE INFORMATION

NW Holdings and NW Natural file annual, quarterly and current reports and other information with the Securities and Exchange Commission (SEC). The SEC maintains an Internet site where reports, proxy statements, and other information filed can be read, copied, and requested online at its website (www.sec.gov). In addition, we make available, free of charge, on our website (www.nwnaturalholdings.com), our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K,

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and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) and proxy materials filed under Section 14 of the Securities Exchange Act of 1934, as amended (Exchange Act), as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. We intend to use our website as a means of disclosing material non-public information and for complying with our disclosure obligations under Regulation FD. Accordingly, investors should monitor our website, in addition to following our press releases, SEC filings and public conference calls and webcasts. We have included our website address as an inactive textual reference only. Information contained on our website is not incorporated by reference into this annual report on Form 10-K.

NW Holdings and NW Natural have adopted a Code of Ethics for all employees, officers, and directors that is available on our website. We intend to disclose revisions and amendments to, and any waivers from, the Code of Ethics for officers and directors on our website. Our Corporate Governance Standards, Director Independence Standards, charters of each of the committees of the Board of Directors, and additional information about NW Holdings and NW Natural are also available at the website. Copies of these documents may be requested, at no cost, by writing or calling Shareholder Services, Northwest Natural Holding Company, 250 S.W. Taylor Street, Portland, Oregon 97204, telephone 503-220-2402.