On sunny days in the Hill Country, Tom Cook taps open an app on his phone and watches the power generated from the solar panels on his roof flow to his home — and out to the state power grid.

Cook has a battery storage system on the side of his home in Bandera to power things during outages. The rest of the time, his retail electric provider sends power from his battery back to the grid.

In turn, he gets a monthly bill credit and a sense of community service in supporting the grid.

“We get the sun beaten down on us, and it’s good to have the sun pay us back,” Cook said.

Cook, 72, installed solar panels and a battery in September as part of a program offered by his retail electric provider, Bandera Electric Cooperative.

Along with Tesla, Bandera Electric, a small co-op based in the so-called Cowboy Capital of the world, qualified for a state pilot program to show how everyday Texans could participate directly in the wholesale power market.

The companies facilitate that participation by pulling together small energy resources spread across communities — like residential solar panels and batteries, smart thermostats and the batteries in electric vehicles — and funneling that extra power to the state grid when the Electric Reliability Council of Texas, the primary grid operator, signals a need for it.

The result is what’s called a “virtual power plant” — a burgeoning resource that, across the state, has the potential to send thousands of megawatts of energy back to the grid in moments of crisis.

“It’s just another tool in the toolbox for ERCOT to switch on and off,” Matthew Boms, executive director of the Texas Advanced Energy Business Alliance, said. “It gives us as much resources as a traditional power plant would, and those are technologies that a lot of folks in Texas are already using.”

Cook’s home is one of 34 currently enrolled in Bandera Electric’s virtual power plant, a small but growing collection of batteries that can offer the grid about 0.5 megawatts at a time.

Three virtual power plants — known as aggregated distributed energy resources, or ADERs — totaling 25.5 megawatts have been approved so far as part of the state’s pilot project. (ERCOT estimates that 1 megawatt of electricity can power around 250 homes.)

“We know that there are these resources out there in Texas homes, in Texas businesses,” said Amy Heart, senior vice president of policy at Sunrun, a home solar and battery company. “We know we need every electron to help this grid and to meet the soaring electricity demand.”

ERCOT has estimated that energy demand could nearly double by 2030 — a massive surge driven by population growth, increasingly severe weather in Texas, an influx of large commercial users such as data centers and cryptocurrency mines and the electrification of oil and gas operations.

In August, ERCOT appeared to hit a record demand level of 85.6 gigawatts. Last week, the grid operator predicted that in a worst case scenario, the grid may not have enough energy supply to meet peak demand beginning in summer 2026.

Meeting that demand will require new generation sources and more transmission infrastructure to carry that power around the state.

The Legislature’s recent efforts to add new natural gas-powered generation and to build out transmission lines will take years to develop. Pulling unused power from homes and businesses with battery storage and power-saving technology can put energy back on the grid immediately, boosting the grid’s resiliency and paying those customers for helping out.

Bandera Electric and Tesla are fine-tuning the way this can work through the state’s pilot project, and other electricity companies have created their own virtual power plants through so-called demand response programs — by lowering their customers’ energy use when demand is high.

Put together, experts estimate that there are several gigawatts of power in Texas waiting to be tapped into, sitting behind the meter in people’s homes and businesses. In 2023, the Public Utility Commission said they amounted to 2.3 gigawatts across the state. That number has certainly grown since.

A typical nuclear power plant produces 1 gigawatt of electricity, which can power roughly 250,000 homes.

Nationally, the amount of residential solar installed each year equals about seven or eight nuclear power plants, according to Heart. Smart thermostats already installed in Texas could offer the grid up to 2.6 gigawatts, according to Bandera Electric CEO Bill Hetherington.

How does a virtual power plant work?

The state’s ADER pilot project began around three years ago with the goal of demonstrating how coordinated distributed energy resources — the technical name for devices that can send power back to the grid from homes and businesses — could integrate into the energy market as if they were a power plant or solar farm.

Traditionally, electricity is generated at a large scale — such as by power plants and hydroelectric dams — and transported through power lines to homes and businesses. But the expansion of residential solar, batteries and smart thermostats, Boms said, is “flipping that on its head.”

“We have this new technology that allows folks at the distributed level to generate their own electricity, and potentially sell that back to the market,” he said. “It’s a completely new model.”

That growth raises the question of how to coordinate all of those devices, energy consultant Doug Lewin said. “How do you make them contribute to grid reliability, lower costs for everybody — whether they have those resources or not? And that’s really what the pilot is starting to uncover.”

Bandera Electric’s program starts with Apolloware, a real-time energy management platform it developed to help customers control their energy usage. The smart technology monitors how much power a home and each of its devices is using.

Customers can then choose to install solar panels and lease a battery from Bandera Electric. Apolloware then allows the co-op to sell extra power from participating batteries back to the grid.