California’s electric grid operator has approved a 10-year transmission plan that spotlights 23 projects estimated to cost almost $3bn in total for system expansions and upgrades necessary to keep pace with the state’s aggressive transition to renewable energy resources.

The 2021-22 spending ramp compares with an average $217m in transmission spending targeted in plans over the last five years, according to California Independent System Operator (Caiso), which also manages the state’s bulk electricity market.

Caiso noted that the current transmission plan expects that 2.7GW of new resource capacity would be needed annually over the the next decade’s planning horizon versus 1GW in the 2020-21 plan. The 2022-23 plan will likely assume a requirement of more than 4GW per year.

“This plan is part of our ongoing commitment to resource adequacy and transmission sufficiency in California,” said Caiso CEO Elliott Mainzer, citing rapid acceleration in the need for new generation partly driven by the state’s 2045 carbon-free electricity goal.

Senate Bill 100 (100 Percent Clean Energy Act of 2018) mandates that renewable energy and zero-carbon resources supply 60% of all retail electricity sold and state agency electricity needs by 2030. California has the second largest state power market after Texas.

Also spurring demand for clean energy are consumers and other stakeholders, continuing electrification of transportation and other carbon-emitting industries, and higher than anticipated impacts of peak loads shifting to later-day hours when solar resources are unavailable, according to the report.

The 2021-22 plan also outlines the role for a widening and expanding set of diverse resources to meet clean energy goals that will include new out-of-state renewables and offshore wind generation.

Now that it has been approved, the plan will guide collaborative activities for the implementation of the newly approved projects, including initiating a competitive solicitation process for four of the higher-voltage projects.

Last month, Caiso also issued its first 20-year Transmission Outlook designed to provide a framework and longer-term vision for the system’s transmission needs without recommending specific projects for approval.

That planning document forecast the state’s transition to clean electric power will require $30.5bn investment in high-voltage bulk transmission infrastructure by 2040 to tie together a potential 121GW of new battery storage and renewable energy production.