AriSEIA Files Letter in Support of Commercial Storage Rate

Arizona Corporation Commission
1200 W. Washington Street
Phoenix, AZ 85007

Re: Arizona Public Service (APS) E-32 L SP Tariff, Docket E-01345A-22-0281

Madam Chair and Commissioners,

Pursuant to Decision No. 78317,1 APS was ordered to engage with stakeholders, namely the Arizona Solar Energy Industries Association (AriSEIA) and the Solar Energy Industries Association (SEIA), to redesign the E-32 L SP (Storage Pilot) rate tariff to increase customer adoption of the 35 MW commercial pilot program. AriSEIA appreciated the opportunity to provide constructive feedback and generally guide the tariff design process towards a solution that creates value for APS and the adopting customers.

Throughout the duration of 2022, AriSEIA met monthly with APS and reiterated that rate optionality and investment certainty are key components of behind-the-meter energy storage adoption as not all customer loads are created equal, and few customers are able to benefit from existing tariffs using 15-minute interval demand charges. To that end, we collaborated with APS on the proposed volumetric, time-of-use (TOU) rate including a substantial differential between on-peak and off-peak rates which de-risks the customer’s energy storage investment in terms of achieving monthly savings while creating grid support during the utility’s coincident peak periods. Our assessment of the new rate tariff is that it will encourage participation in the pilot energy storage program through market-competitive payback opportunities. This rate tariff may also provide a foundation to develop more value-stacking opportunities for utilities such as distributed virtual power plants or similar grid-response programs.

While the proposed E-32 L SP pilot revisions are a significant step in the right direction, we believe that further alignment with APS’ true coincident on-peak demand periods is important to creating an equitable program. To this end, we issued our recommendation to APS to limit the on-peak hours to Monday through Friday in lieu of across all seven (7) days of the week as the weekend load and marginal prices are typically much lower and do not merit the same TOU price differential. We look forward to continuing to work with APS as this program evolves.

Thank you for considering these comments and we encourage you to adopt this rate in the first quarter of 2023 and to continue promoting more grid-interactive programs for customer-sited distributed energy resources.

Respectfully,

Autumn Johnson
Executive Director
AriSEIA
520-240-4757
autumn@ariseia.org

John Mitman
President, Board of Directors
AriSEIA
480-251-2934
john@ariseia.org

1 Arizona Corporation Commission, Decision 78317, November 9, 2021, available here https://docket.images.azcc.gov/0000205236.pdf?i=1670984264693.