2021 Avista Natural Gas IRP DRAFT Safe Harbor Statement This document contains forward-looking statements. Such statements are subject to a variety of risks, uncertainties and other factors, most of which are beyond the Company’s control, and many of which could have a significant impact on the Company’s operations, results of operations and financial condition, and could cause actual results to differ materially from those anticipated. For a further discussion of these factors and other important factors, please refer to the Company’s reports filed with the Securities and Exchange Commission. The forward- looking statements contained in this document speak only as of the date hereof. The Company undertakes no obligation to update any forward-looking statement or statements to reflect events or circumstances that occur after the date on which such statement is made or to reflect the occurrence of unanticipated events. New risks, uncertainties and other factors emerge from time to time, and it is not possible for management to predict all of such factors, nor can it assess the impact of each such factor on the Company’s business or the extent to which any such factor, or combination of factors, may cause actual results to differ materially from those contained in any forward- looking statement. TABLE OF CONTENTS 0 Executive Summary 1 Introduction 2 Demand Forecasts 3 Demand Side Resources 4 Supply Side Resources 5 Carbon Reduction 6 Integrated Resource Portfolio 7 Alternate Scenarios, Portfolios, and Stochastic Analysis 8 Distribution Planning 9 Action Plan Executive Summary Executive Summary Avista’s 2021 Natural Gas Integrated Resource Plan (IRP) identifies a strategic natural gas resource portfolio to meet customer demand requirements over the next 20 years. While the primary focus of the IRP is meeting customers’ needs under peak weather conditions, this process also evaluates customer needs under normal or average conditions. The formal exercise of bringing together customer demand forecasts with comprehensive analyses of resource options, including supply-side resources and demand-side measures, is valuable to Avista, its customers, regulatory agencies, and other stakeholders for long-range planning. Benefits of Natural Gas For Customers: Natural gas is affordable, resilient, and reliable. For Society: Natural gas is an abundant energy resource produced in North America, which helps lessen our dependency on foreign oil. For Innovation: Natural gas can play a supporting role in expanding the use of renewable energy sources. For Environment: Natural gas is the cleanest burning fossil fuel, so it helps reduce smog and greenhouse gas emissions. For Economy: Natural gas provides nearly a fourth of North America's energy today. IRP Process and Stakeholder Involvement The IRP is a coordinated effort by several Avista departments with input from our Technical Advisory Committee (TAC), which includes Commission Staff, peer utilities, customers, and other stakeholders. The TAC is a vital component of our IRP process that provides a forum for discussing multiple perspectives, identifies issues and risks, and improves analytical planning methods. TAC topics include natural gas demand forecasts, price forecasts, demand-side management (DSM), supply-side resources, modeling tools, distribution planning, and policy issues. The IRP process produces a resource portfolio designed to serve our customers’ natural gas needs while balancing cost and risk. Planning Environment A long-term resource plan addresses the uncertainties inherent in any planning exercise. Natural gas is an abundant North American resource with expectations for ample supplies for many decades because of continuing technological advancements in extraction. The Avista Corp Draft 2021 Natural Gas IRP 1 Executive Summary use of natural gas in liquefied natural gas (LNG) exports, power generation and exports to Mexico will continue to add demand for natural gas. In addition to fossil fuel natural gas, renewable natural gas and hydrogen are considered vital toward any carbon reduction goal, but currently not as readily available. All future scenarios carry risk based on unknown prices and expected resources. To account for risk associated with these uncertainties, we model various sensitivities and scenarios to account for the risks in supply and demand. Demand Forecasts Avista defines eleven distinct demand areas in this IRP structured around the pipeline transportation and storage resources that serve them. Demand areas include Avista’s service territories (Washington; Idaho; Medford/Roseburg, Oregon; Klamath Falls, Oregon and La Grande, Oregon) and then disaggregated by the pipelines serving them. The Washington, Medford and Idaho service territories include areas served only by Northwest Pipeline (NWP), only by Gas Transmission Northwest (GTN), and by both pipelines. Weather, customer growth and use-per-customer are the most significant demand influencing factors. Other demand influencing factors include population, employment, age and income demographics, construction levels, conservation technology, new uses, and use-per-customer trends. Customers may adjust consumption in response to price, so Avista analyzed factors that could influence natural gas prices and demand through price elasticity. These factors include: • Supply: shale gas, industrial use, and exports to Mexico and of LNG. • Infrastructure: regional pipeline projects, national pipeline projects, and storage. • Regulatory: subsidies, market transparency/speculation, and carbon regulation. • Other: drilling innovations, thermal generation and energy correlations (i.e. oil/gas, coal/gas, and liquids/gas). Avista developed a historical-based reference case and conducted sensitivity analysis on key demand drivers by varying assumptions to understand how demand changes. Using this information, and incorporating input from the TAC, Avista created alternate demand scenarios for detailed analysis. Table 1 summarizes these demand scenarios, which Avista Corp Draft 2021 Natural Gas IRP 2 Executive Summary represent a broad range of potential scenarios for planning purposes. The Average Case represents Avista’s demand forecast for normal planning purposes. The Expected Case is the most likely scenario for peak day planning purposes. Table 1: Demand Scenarios 2021 IRP Demand Scenarios Average Case Expected Case High Growth, Low Price Low Growth, High Price Carbon Reduction The IRP process defines the methodology for the development of two primary types of demand forecasts – annual average daily and peak day. The annual average daily demand forecast is useful for preparing revenue budgets, developing natural gas procurement plans, and preparing purchased gas adjustment filings. Forecasts of peak day demand are critical for determining the adequacy of existing resources or the timing for new resource acquisitions to meet our customers’ natural gas needs in extreme weather conditions. Table 2 shows the Average and Expected Case demand forecasts: Table 2: Annual Average and Peak Day Demand Cases (Dth/day) Annual Average Peak Day Non-coincidental Year Daily Demand Demand Peak Day Demand 2021 95,126 363,586 349,210 2040 102,054 407,216 388,615 Annual Average Daily Demand – Expected average day, system-wide core demand increases from an average of 95,126 dekatherms per day (Dth/day) in 2021 to 102,054 Dth/day in 2040. These numbers are net of projected conservation savings from DSM programs. Appendix 3.1 shows gross demand, conservation savings and net demand. Peak Day Demand – The peak day demand for the Washington, Idaho and La Grande service territories is modeled on and around February 28th of each year. For the southwestern Oregon service territories (Medford, Roseburg, Klamath Falls), the model assumes this event on and around December 20th of each year. Expected coincidental peak day, or the sum of demand from each territories modeled peak, the system-wide core demand increases from a peak of 363,586 Dth/day in 2021 to 407,216 Dth/day in Avista Corp Draft 2021 Natural Gas IRP 3 Executive Summary 2040. Forecasted non-coincidental peak day demand, or the sum of demand from the highest single day including all forecasted territories, peaks at 349,210 Dth/day in 2021 and increases to 388,615 Dth/day in 2040. This is also net of projected conservation savings from DSM programs. Figure 1 shows forecasted average daily demand for the five demand scenarios modeled over the IRP planning horizon. Figure 1: Average Daily Demand (Net of DSM Savings) Figure 2 shows forecasted system-wide peak day demand for the five demand scenarios modeled over the IRP planning horizon. Avista Corp Draft 2021 Natural Gas IRP 4 Executive Summary Figure 2: Peak Day Demand Scenarios (Net of DSM Savings) Natural Gas Price Forecasts Natural gas prices are a fundamental component of integrated resource planning as the commodity price is a significant element to the total cost of a resource option. Price forecasts affect the avoided cost threshold for determining cost-effectiveness of conservation measures. The price of natural gas also influences the consumption of natural gas by customers. A price elasticity adjustment to use-per-customer reflects customer responses to changing natural gas prices. Avista expects carbon legislation at the state level through a cap and reduce (Oregon) or social cost of carbon tax mechanism (Washington). Current IRP price forecasts include a considerably higher carbon adder in Oregon and Washington, but no carbon