Electric Vehicle-Grid Integration with Dr. Carla Peterman – California China Climate Institute

Audio by: Megan Bergeron | Writing by: Marie Hogan, Amanda Neslund, Alexandra Jade Garcia  | Socials by: Wangyuxuan Xu

How does transitioning to renewable energy challenge the electric grid?

As of 2020, California’s non-CO2 emitting energy share is 51 percent, the majority of which is renewable, and legislation passed in 2018 mandates that this reaches at least 60 percent by 2030. This supports emissions reductions goals set by SB 32, the 2016 update to prior 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 to function using carbon emitters like coal or natural gas. The majority of California’s renewable energy comes from solar and wind. Solar and wind energy generation vary depending on the time of day and season, among other factors. Compared to traditional fuel sources, the amount of energy they supply day-to-day isn’t as easy to predict or transfer from one location to another.

Because the US electrical grid lacks the infrastructure necessary to store large amounts of energy, 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 that energy to the electric grid has seen a large growth in the share of power provided by renewables, electric vehicle (EV) sales have shot to 60 times higher than they were a decade ago and continue to rise, increasing by 85 percent from 2020 to 2021 alone. The majority of electric vehicles sold are plug-in electric vehicles, so called because they charge by plugging into the electric grid via charging stations. 

The growth of electric vehicles has increased the demands on the electric grid, which can be a particular problem if EV owners charge their cars at the same time that other electricity demand is at its peak.  But EVs may also be part of the solution to some of the challenges of operating the grid. 

Why might electric vehicles be a solution?

California’s rapid transition to renewables combined with the growth of electric vehicles pose challenges to California’s electric grid, but both are essential to the State’s effort to reduce greenhouse gas emissions. Strategic use of vehicle-grid-integration (VGI) can offer a solution to these problems.

While EVs have traditionally been unidirectional, meaning they can only take energy from the grid, VGI allows energy stored in car batteries to be sent back to the electricity grid by “discharging” during times of elevated demand. Proponents argue that integration of this technology would improve the electrical grid’s ability to maintain an equilibrium between energy supply and demand. 

VGI can also manage the amount of electricity flowing to plug-in EVs when the grid is stressed. While bidirectional vehicles augment energy storage capacity, increasing the total energy supply available, electrical meters on EV charging stations would reduce the risk of too much demand at any one time, turning off or reducing charging when the grid is faced with high demand. 

Although VGI has been proposed for years, it is just now starting to be put into practice. In 2019, California adopted SB 676, which requires that the Public Utilities Commission (CPUC), which oversees the electric grid statewide, “maximize the use of feasible and cost-effective electric vehicle grid integration” by 2030. The CPUC already has numerous VIG projects underway, including an initiative to incentivize EV discharging intended to reduce the risk of power outages during extreme weather events like the heat waves experienced in 2020 and 2021. In addition to PUC-led integration projects, utility companies like Pacific Gas and Electric (PG&E), which provides electricity for almost half of California residents, have programs implementing vehicle-grid integration.

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.

Links to Learn More

Pew: Electric Cars Will Challenge State Power Grids

Grist: Your electric vehicle could become a mini power plant

Emerging Tech Brew: California’s vehicle-to-grid experiments offer a glimpse of the future


Dr. Peterman: Transportation is our biggest contribution to greenhouse gasses in the state. So the more we can electrify our vehicles, then that can actually have some real impact.

Ethan: That’s Dr. Carla Peterman, chief sustainability officer at electric utility Pacific Gas and Electric and a former California energy official, in a California-China Climate Institute conversation with former Governor Jerry Brown. She wants to improve the electric grid to handle more electric vehicles.

Dr. Peterman: When you put one electric vehicle on the grid,  it’s equivalent to about the load of two households. If you’re having supply constraints, it can become a reaction to go back to the fossil fuel that you know is going to be available. The environmental cost and the health cost just aren’t worth it – So we’re going to need to improve our grid infrastructure to accommodate that move. 

Ethan: The batteries in the vehicles themselves might provide a solution.

Dr: Peterman: The ability to plug your vehicle into your home, to serve as backup energy,  at times when the system needs it, or to have your vehicle send power back to the grid, those are all areas that we’ve been talking about for years

but given the needs that we’re seeing, the technical feasibility is starting to become reality. So we’re partnering with car companies, talking to other utilities. About how we can use vehicles in multiple ways on our grid. In addition to as a driving resource.

Ethan: To learn more about Dr. Peterman and how electric vehicles can provide grid services, visit climatebreak.org. I’m Ethan Elkind and this was Climate Break.

Electric Vehicle-Grid Integration with Dr. Carla Peterman – California China Climate Institute