AVISTA CORP

Our environmental issues and contingencies disclosures have not materially changed during the nine months ended September 30, 2026 except as follows:

Presidential Executive Action

On March 16, 2026, the President of the U.S. issued an Executive Order entitled “Removing Regulatory Barriers to Affordable Home Construction,” with the stated objective of increasing housing supply and affordability by reducing federal, state and local regulatory requirements that the Administration views as increasing construction costs and slowing development. Among other things, the Executive Order directs various federal agencies to incentivize state and local governments to eliminate mandatory green or energy-efficient building codes, review and potentially eliminate “unduly burdensome or costly” federal energy efficiency requirements, revise permitting rules relating to stormwater, wetlands and water pollution controls, and shorten environmental review timelines for housing projects.

On April 20, 2026, the President of the U.S. issued several Executive Orders invoking authority under the Defense Production Act of 1950 (DPA) to (a) designate oil production and storage, coal and natural gas related power generation activities, electric facilities and supply chains, and large scale energy and energy-related infrastructure as critical resources under the DPA and (b) authorize the Department of Energy to use its authority under the DPA to expand and accelerate domestic capacity in each of these areas.

We are evaluating the extent to which potential changes from these Executive Orders may affect our financial results and operations.

EPA Endangerment Finding Revocation and Rescission of Carbon Pollution Standards

In February 2026, the EPA formally revoked its 2009 Endangerment Finding, which was a landmark determination that six key greenhouse gases, including carbon dioxide and methane, threaten the public health and welfare of current and future generations. The Endangerment Finding provided the scientific and legal foundation for federal regulation of those identified greenhouse gases, including regulation of the release of greenhouse gases from power plants and other significant emissions sources.

In September 2026, the EPA issued a final rule, repealing most provisions of the 2024 Carbon Pollution Standards for greenhouse gas emissions from fossil fuel-fired electric generating units, eliminating most carbon capture and storage-based requirements and emissions guidelines established in 2024.

The EPA’s decision and rulemaking have been the subject of future legal challenges, the outcome of which cannot be predicted. The precise extent of that deregulation, as well as any potential impact on the Company’s operations, cannot be determined at this time.

Washington Legislation and Regulatory Actions

Washington State Building Codes

In April 2022, the Washington State Building Code Council (SBCC) approved a revised energy code requiring most new commercial buildings and large multifamily buildings to install all-electric space heating. An amendment to the code allows for natural gas to supplement electric heat pumps. In addition, in November 2022, the SBCC approved new building and energy codes for residential housing, requiring new residential buildings in Washington to use electricity as the primary heat source.

Both the commercial and residential building and energy codes were the subject of legal challenges in both Washington State Superior Court (the State Action) and in the Federal District Court for the Eastern District of Washington (the Federal Action). The State

Action remains pending and the plaintiffs in the Federal Action subsequently dismissed the action, without prejudice to their ability to refile after the SBCC rulemaking process is complete.

In May 2024, we, along with Cascade Natural Gas Corporation, Northwest Natural Gas Company, and a coalition of homebuilders, heating unit dealers and other parties, filed a lawsuit challenging the approved building codes on the grounds that they are preempted by the Energy Policy and Conservation Act (EPCA). The lawsuit was filed in the United States District Court for the Western District of Washington. In September 2026, the Court ruled that the SBCC is immune from suit because it is not responsible for directly the codes and ordered dismissal of the litigation.

In November 2024, Washington voters approved Initiative 2066, which would prohibit state and local governments from restricting access to natural gas, prohibit the SBCC from discouraging or penalizing the use of natural gas, and prohibit the WUTC from approving any multi-year rate plan that requires or incentivizes natural gas companies to terminate or limit natural gas service. Opponents of the Initiative filed suit in Washington state court challenging the validity of the Initiative, while proponents of the Initiative filed suit in Washington state court to require the SBCC to comply with the new law. In July 2026, the Washington Supreme Court resolved both lawsuits by ruling that Initiative 2066 violated the single subject rule and was therefore unconstitutional.

Over time, the building code changes, if ultimately upheld, would likely have an adverse impact on our natural gas business and natural gas customers but could also have a positive effect on our electric business. While we are in the process of studying the implications of the changes on our business, at this time we are not able to quantify the likely net effect, positive or negative, on our overall results of operations over the long term. However, the changes would require that additional generating capacity be available to utilities and customers in Washington state.

Oregon Legislation and Regulatory Actions

Climate Protection Plan

In March 2020, Oregon Governor Kate Brown issued Executive Order No. 20-04, “Directing State Agencies to Take Actions to Reduce and Regulate Greenhouse Gas Emissions.” The Executive Order launched rulemaking proceedings for Oregon agencies with jurisdiction over GHG-related matters, with the aim of reducing Oregon’s overall GHG emissions to 80 percent below 1990 levels by 2050. This Executive Order led to the Oregon Department of Environmental Quality (ODEQ) developing cap and reduce rules known as the CPP. The CPP originally became effective in January 2022, but was subsequently challenged and declared invalid on procedural grounds. Thereafter, the ODEQ reissued the CPP in November 2024 with updated compliance periods.

On April 16, 2026, approximately 30 parties, consisting of businesses, utilities, trade associations and unions, filed a Petition challenging the repromulgated version of the CPP. Avista Corp. is a party to the litigation, which remains pending.

See the 2025 Form 10-K for further discussion of our environmental issues and contingencies.