California's Grid Has a Safety Cushion on Its Hottest Day
Data Centers Have Asked for Nearly All of It
Every power grid needs a safety cushion, extra capacity beyond what customers are using, so the lights stay on when demand spikes. On California's hottest days, that cushion is what keeps the system running.

How big is the cushion?
During a heat wave in September 2026, California's grid operator reported about 67,600 megawatts of available capacity. The state's all-time record demand is 52,061 megawatts, set in September 2022. On a record-breaking day, that leaves roughly 15,500 megawatts of cushion. Data center developers have asked PG&E for about 15,000 megawatts of power. That is nearly the entire cushion.

An important caveat
This does not mean the grid is about to collapse. Many data center requests are speculative and will not all be built, and the state continues to add new generation and storage. Signed agreements reached about 4,000 megawatts by the end of 2025, still a significant amount. But the comparison shows how quickly new demand can eat into the margin California relies on during its hardest days.

Why the tightest hours matter
California's grid operates at well below its maximum most of the time. The strain shows up during hot evenings, when solar production fades and air conditioners keep running. Data centers run around the clock, so their demand adds to those tight hours instead of avoiding them. The tighter those hours get, the more expensive they become, and the more valuable it is to not depend on the grid during them.

Batteries are already part of the answer
California now has about 21,000 megawatts of battery storage supporting its grid, up from less than 700 megawatts in 2019. That is roughly a third of peak demand. Batteries store solar energy during the day and release it during the evening peak.
A home battery does the same thing on a smaller scale. It stores your solar power and uses it during the most expensive hours. When you have extra, your system can send power back to the grid and earn credits. California's SB 913 directs regulators to value battery power sent to the grid during high demand.

Choosing your side of the meter
Some homeowners do not like the idea of supplying a grid that serves data centers. But on the hottest days, homes with stored power are not competing for the shrinking cushion. They are adding to it. Qualifying homeowners can get solar and battery storage through third-party ownership programs without buying or financing equipment.

The takeaway
California's safety cushion is shrinking as demand grows. Homeowners can build their own cushion at home, with savings that can reach up to 40 percent compared with utility rates, depending on the home and program.

To find out if your home qualifies for a TPO solar and battery program, visit myhomesolution.org/california_public_utility_commissions