For 18 days in a row this fall, Puerto Rico's grid drew extra power from thousands of home batteries to avoid straining the system during a stretch of extreme heat.

The homes behind that backup power belong to a rapidly expanding network of Sunrun customers, who get paid for sharing stored electricity and decide how much to keep back for their own outages.

Here's what to know

Sunrun's virtual power plant in Puerto Rico now serves more than 60,000 customers, twice as many as before, according to Electrek. The company said nearly 70,000 batteries are now hooked into the system, letting it draw on equipment scattered across thousands of homes and send that power to the grid all at once.

Sunrun said the daily deployments began on Oct. 13 when a heat spike drove demand.

Customer participation grew nearly eightfold between 2024 and 2025, climbing from about 4,000 to more than 30,000, and Sunrun has tapped the batteries more than 60 times since April, Electrek reported. Those batteries typically supply 45 megawatts for 4-hour stretches.

For homeowners exploring storage, EnergySage offers a resource for comparing battery products and competitive installation estimates, a starting point for weighing equipment costs against backup needs and potential earnings.

EnergySage also partners with electrification company Qmerit. It can help homeowners find the best available battery-storage pricing.

More background

According to the U.S. Energy Information Administration, the island's average residential electricity price in August was 26.36 cents per kilowatt-hour, versus 18.16 cents nationally. Those high bills don't spare Puerto Rico residents from persistent power outages.

The agency's data put the average Puerto Rico outage time at 36 hours in 2025, a 19% jump from 2024, not counting major storms or other large-scale events. Mainland customers, by contrast, lose power for about 2 hours a year on average under the same measure.

Major storms and other big disruptions tacked on 23 more hours of lost power across the island, the EIA said.

The battery-sharing effort doesn't stop at Sunrun. Grid operator LUMA said its Customer Battery Energy Sharing program, which includes more than 90,000 customers, had delivered roughly 75 MW when the island's supply ran short.

What can be done?

Most participants keep the bulk of their battery's capacity for themselves and offer up only a slice of it, Sunrun said.

Companies in the program automatically manage how each battery responds once LUMA sends out a request, per Electrek. LUMA taps the program when it expects demand or reserve needs to outpace the electricity available at the time.

Equipment configured for off-grid use can also give residents greater energy independence.

For households seeking a smaller-scale backup option, Pila offers a plug-and-play alternative at a substantially lower price than whole-home backup systems.

Where can I learn more?

Home batteries can keep the power on during outages and help support the grid in Puerto Rico and beyond.

• A Massachusetts homeowner learned virtual power plant payments could bring in about $1,000 annually.

• In California, Sunrun and Tesla tapped 140,000 home batteries to supply 580 MW.

• In Vermont, 5,500 leased home batteries became the state's biggest power source.

• Puerto Rico apartment residents use solar and battery backup to weather blackouts without generators.

• Homeowners can recharge batteries from the grid, and one weathered a weeklong outage.

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