Grant PUD Considers 20-Year Deal for Royal Slope Solar and Battery Project

EPHRATA — Grant County PUD commissioners are reviewing a proposed 20-year power purchase and energy storage agreement that would add 260 megawatts of new solar and battery capacity to the utility’s portfolio by 2028.

Under the proposal, Grant PUD would buy power from Royal Slope Solar LLC — a soon-to-be developed solar project northeast of Wanapum Dam — and enter a parallel contract with Royal Slope BESS for 260 megawatts of lithium-ion battery storage capable of holding a four-hour charge. Both projects would be built on leased land and connect to existing Bonneville Power Administration transmission infrastructure through the Columbia and Rocky Ford substations.

Vice President of Energy Supply and Marketing Rich Flanigan told commissioners the agreements would begin no earlier than March 1, 2028, for the solar component and April 1, 2028, for the battery storage. The cost of solar energy would range from $65 to $75 per megawatt-hour, while battery storage would run between $14 and $16.50 per kilowatt-month — both within the utility’s requested price range.

Flanigan said the project would help Grant PUD meet its Integrated Resource Plan goals for renewable energy and storage capacity by 2028 and secure a reliable energy supply through 2030. Any remaining power needs would be filled through additional agreements or wholesale market purchases.

Royal Slope Solar LLC is a subdivision of Clearway Energy Group, a national energy developer with more than 350 projects across the country. The Royal Slope project was among 82 proposals submitted to Grant PUD in 2023 as part of its plan to ensure long-term energy stability while moving toward Washington’s 2045 goal of eliminating carbon emissions from the state’s energy grid.

The same request for proposals also produced two other solar contracts: the 80-megawatt Goose Prairie Solar project near Yakima and the 120-megawatt Quincy Solar project on land near the Ephrata Municipal Airport.

Commissioners are expected to vote on the Royal Slope Solar and BESS agreements at their next meeting on October 28.