The “too much of a good thing” rule may be proving true in California’s electricity market as the state faces looming power shortfalls beginning next year after aggressive moves to cut greenhouse gas emissions also curbed power output.

The state may be hit with a 4.7 gigawatt capacity shortfall in three years during September evenings, which may force it to slow the switch to clean power to avoid blackouts. A gigawatt is roughly equivalent to the power needed for a million homes for a year. 

The state has set ambitious targets to curb greenhouse gasses, and the power sector has made most of the cuts needed to meet these goals. Natural gas and coal-burning power plants have been shuttered or revamped while the number of solar and wind installations has mushroomed. But electricity storage capacity hasn’t kept pace with the increase in renewable supplies and demand has stagnated.

The shortfall could reach maximum levels of 2,300 MW next year, 4,400 MW in 2021, and 4,700  in 2022 during early evenings in September, the California Independent System Operator said in an Aug.12 note filed with the California Public Utilities Commission. The grid operator recommended the state rethink the schedule for closing some coastal gas-fired generation plants as part of a ban on the use of seawater-cooled electric facilities.

Natural gas plants are still needed to make up for gaps in the flow of electricity from renewable sources that usually occur for a few hours a day, when high demand coincides with a drop in solar and wind energy because the sun isn’t out or the wind has died. For instance, at AES’s Alamitos operations in Long Beach, the old units can produce 1,900 megawatts but run at only about 5% of capacity. This facility is in the process of being replaced by a more-efficient 1,040 megawatt capacity plant that uses less seawater for cooling.

“If California doesn’t delay the Alamitos OTC units closure at the end of 2020, then the SoCal Area will be very short of capacity, especially when you also include the interaction with Arizona, which is losing the 2250 MW Navajo coal plant at the end of 2019,” Wade Schauer, Wood Mackenzie research director, Americas power & renewables, told Karma.

The old model where utilities delivered electricity to a captive public and the grid itself is being disrupted by solar panels sprouting on rooftops. California is in the forefront of these changes, as efficiency regulations have curbed energy use while utilities are ahead of schedule in switching renewable sources. 

Renewable energy is vulnerable to weather changes, which can throw the grid off balance. Renewables lack what power planners most value: the ability to be used when needed and quickly turned off when not. Solar, for example, is plentiful in the middle of the day. There’s so much that most days the California pays its neighbors to take some because the excess would impede the grid’s constant need for balance.

“I’m sure there will be a push for more battery storage but I don’t know if that much can be built by 2021/2022,” Schauer said. “Other than enabling storage, new/incremental solar adds very little to system reliability in California now.”

To get California to its goal of operating on 100% clean energy by 2045 will require a shift in how electricity is produced and managed. There will have to be a greater reliance on stored power at higher efficiency and lower cost. The state got 33% of its electricity from renewable sources in 2018, the California Energy Commission estimates, not counting solar panels on rooftops, which would add several more percentage points. 

The state has made great strides in efficiency, but more will have to occur for the goal to be met. California’s total energy consumption is the second-highest in the U.S., but it’s per capita consumption ranked 48th, at least in part due to its mild climate and energy-efficiency programs, Energy Information Administration data show.

While California is taking the lead in cutting greenhouse-gas emissions, the transition isn’t without problems. Regulators and government officials will need to proceed cautiously as an overambitious timetable might threaten the reliability of the state’s electric grid, resulting in a slowdown in change to a sustainable future.