Austin Energy details renewables and batteries; commissioners press for contract-level battery economics

Lisa Martin, chief operating officer at Austin Energy, told the Resource Management Commission the utility is adding a mix of solar, batteries, wind and an experimental geothermal pilot as part of its Resource Generation and Climate Protection Plan to 2035.

"The electricity that was generated by Austin Energy in the last year was 73% carbon free," Martin said, adding that represented roughly 65% of customer load and that new procurements are intended to raise that share. She highlighted recent and proposed projects including an 8-megawatt landfill solar project at FM 812, roughly 25 megawatts of solar on city facilities, and an existing solar portfolio approaching a gigawatt across Texas. On batteries, Martin said council recently approved a 100-megawatt four-hour battery (expected online by 2027), a 40-MW 1.5-hour battery, and the utility has brought forward a 100-MW 2-hour battery agreement this week, which together would bring utility-scale battery capacity to about 240 MW. She also noted two wind contracts totaling just under 300 MW and a 9.9-MW geothermal pilot in West Texas.

Commissioners pressed Martin on battery economics. Vice Chair Robbins presented benchmarking slides and asked Austin Energy to "describe the business model that makes these storage contracts economic," citing public benchmark studies and apparent deltas between wholesale prices and contract payments. Martin replied that many contract details are treated as competitive matters and cannot be discussed in detail in open session but described the general value case: charging at low prices and discharging at high prices and capturing other operating value streams. "In each one of them, if we're coming forward after we do our analysis, it's because the operating characteristics and the pricing terms... ultimately lead to a proposal that is a value add for our customers," she said.

Robbins suggested the commission consider an executive session or a joint session with the Electric Utility Commission to review competitive details and asked that "any large renewable contract or any battery contract be brought to our commission for review and comment to city council." Martin acknowledged the request but said she was restricted from sharing certain competitive details publicly.

There were no formal votes on the portfolio during the meeting. Commissioners also asked about the pathway to 100% carbon-free supply, transmission-import strategies to relieve local congestion, and how distributed batteries and rooftop solar factor into the plan.