Balancing the Grid: California’s Shift to Renewable Energy Sources

Transformers in the California desert with yellow desert flowers in the foreground

Image caption: California’s ambitious goal to achieve 60% renewable energy by 2030 brings new challenges in managing grid stability due to the variable nature of solar and wind energy.  Image Credit: Bob Wick, Bureau of Land Management / Openverse

Script by: Megan Chan | Audio by: Keya Pardasani | Blurb by: Amanda Neslund

How does transitioning to renewable energy challenge the electric grid?

As of 2022, renewable and non-greenhouse gas emitting sources accounted for 52% of California’s in-state electricity generation with the remaining 48% fueled by natural gas. Legislation passed in 2018 mandates that the state must reach at least 60% renewable energy by 2030 which California is quickly on its way to meet. The 60% goal adds ambition to the emissions reduction goals set by SB 32, the 2016 update to prior landmark climate legislation that required California to reduce its emissions to 40 percent below 1990 levels by 2030. 

Transitioning to reliance on renewable energy sources introduces new challenges to the electrical grid, which was designed primarily around gas-fired power plants that can operate 24 hours a day.  The majority of California’s renewable energy comes from solar and wind. Such renewable energy generation varies depending on the time of day and season, among other factors. Compared to gas-fired power plants, solar and wind energy isn’t as predictable or transferable from one location to another.

With limited energy storage capacity, the US electrical grid lacks the infrastructure necessary to store large amounts of energy, so the variability of wind and solar energy makes it more challenging to balance energy supply and demand in real-time, which is an essential function of the energy system. As a result, the energy system design must evolve to meet the challenges of solar and wind variability, particularly during periods of peak demand, in order to ensure grid stability and sufficient energy support.  

At the same time, California’s energy grid has seen a large growth in demand due to the electrification of the transportation and residential sectors. Electric vehicle (EV) sales are 60 times higher than they were a decade ago and continue to rise, increasing by 85% from 2020 to 2021 alone. In 2023, EV sales in California account for 25% of EVs sold in the US. California has also enacted higher building energy efficiency standards to help accelerate the decarbonization movement. As of 2023, all new buildings must have at least one heat pump for heating or water heating, or they will face higher energy efficiency requirements. This growth in the prevalence of electric appliances and vehicles has increased the demands on the electric grid. This can be a particular problem if EV owners charge their cars or run their appliances at the same time that other electricity demand is at its peak. A California’s Public Utilities Commission report published in 2023 found the state needs to invest at least $50 billion by 2035 in order to accommodate high adoptions of distributed energy resources associated with transportation and building electrification. 

Energy Storage as a Solution

Improving solar battery storage is vital in accelerating a transition to clean energy as these batteries store solar energy during the day and deliver it back to the grid at night when power is more expensive and carbon-intensive to produce. As of October 2023, California has increased its energy battery storage capacity by 757% to 6,600 megawatts. The state still needs to continue increasing its capacity to 52,000 megawatts to meet clean electricity demands by 2045. These batteries are also especially vital as climate change is increasing the intensity of heatwaves and wildfire seasons leading to increased Public Safety Power Shutoffs (PSPS). During hazardous conditions, electricity companies turn off power circuits to reduce the risk of power lines falling and igniting a wildfire. Solar batteries are one tool to help alleviate the loss of power and can deliver electricity to areas prone to PSPS blackouts. However, large-scale batteries are not a perfect solution as they have considerable environmental costs and require many rare minerals in their production, which have significant associated sustainability and mining costs. Other energy storage technologies from green hydrogen to reservoir storage of hydropower can also help the state meet its energy demands.

About the Guest: Dr. Carla Peterman

As PG&E’s Executive Vice President and Chief Sustainability Officer, Dr. Carla Peterman directs the corporation’s sustainability and regulatory efforts. Previously, Dr. Peterman served as an energy official within the California government, including as CPUC commissioner, where she oversaw their $768 million EV charging infrastructure investment in 2018. Dr. Peterman received a Ph.D. from UC Berkeley’s Energy and Resources Group in 2017, writing her dissertation on state policy for solar energy.

Further Reading


Ethan: I’m Ethan Elkind, and you’re listening to Climate Break. Climate solutions in a hurry. Today’s solution: improving the electricity grid to better support electric vehicles.  Dr. Carla Peterman, Chief Sustainability Officer at Pacific Gas and Electric Company, discussed this need in a conversation with former Governor Jerry Brown, for a California-China Climate Institute conversation.

Dr. Peterman: All the utilities have programs like this. Where we’re also needed to focus right now is actually building up the capacity of the grid because when you put one electric vehicle on the grid, it’s equivalent to about the load of two households.

Ethan: One of the ways to increase electricity capacity is through energy storage, which can store surplus power from solar panels and wind turbines for when the sun isn’t shining, and wind isn’t blowing. Dr. Peterman discussed her work with the California Public Utilities Commission, or PUC, to help boost these storage technologies.

Dr. Peterman: So, one of the things that I was privileged to work on at the PUC was implementation of AB 2514, which directed the PUC to consider setting targets for energy storage. And so California was actually years ahead in terms of setting targets for utilities to build energy storage. So we’ve got a lot of energy storage on our system and that’s allowing us to store some of that sunlight and use it during the evening hours.

Ethan:  To prevent too many electric vehicles from charging when electricity is in short supply, utilities and policy makers are setting rates that make it cheaper for drivers to charge during off-peak hours.

Dr. Peterman: So, the cost of power is cheaper during the day when we have a lot of solar and it gets more expensive later in the day when sun goes down.

Ethan: To learn more about how to fortify and expand the electricity grid for electric vehicles, visit

Balancing the Grid: California’s Shift to Renewable Energy Sources