OREANDA-NEWS. July 19, 2017. The increasing penetration of renewable electricity sources in California causes the state's gas-fired generators to cycle more often, which will lead to higher operating costs, a recent engineering study says.

Renewables caused 21pc of the cycling events for the system's 120 fossil-fueled generators in 2013, up 7.1pc from two years earlier, according to consultant James Schetter, who runs a firm called Renewable Impacts.

Cycling is any change at a power plant like turning the plant on, ramping up or down, or turning it off. Wind power caused the fossil plants to cycle 25pc over those two years, while cycling because of solar power occurred four times more often.

Schetter analyzed hourly data from the California Independent System Operator for the study. Changes in power load were responsible for more than half of the fossil unit cycling, but at 21pc, renewables were the fastest growing cause.

California utilities were required to get 20pc of their electricity from renewable sources in 2013 and 25pc in 2016. The state energy commission concluded late last year that the three major California utilities were 2 percentage points ahead of that goal.

"System load will still be the main driver of cycling," Schetter said. "But load and renewables are in a race to get to number one."

The state's current mandate is a 50pc renewable portfolio standard by 2030, and some state legislators have advanced bills with more aggressive targets.

Almost all of the 120 units in the study were gas-fired, including combined cycle, cogeneration, combustion turbine and steam turbine units.