In early March, strong winds brought down trees and power lines in the Nashville area, leaving thousands of homes without power. But about 20 miles outside the city an electric pickup truck fed energy to John and Rachelle Reigard’s home, keeping their lights on.

“You can look at all the houses around us, and they’re all off,” said Mr. Reigard, who bought the pickup, a Ford F-150 Lightning, more than a year ago. “A lot of people ask the question: ‘How do you have power?’”

The Reigards are part of a small group of pioneers using the batteries in their electric vehicles as a source of backup power for their homes. Energy and auto experts expect many more people to do the same in the coming years as auto and energy companies make it easier for people and businesses to tap the energy in electric cars for more than driving.

Electric grids are increasingly straining and buckling during extreme weather linked to climate change, including in lengthy heat waves, intense storms and devastating floods. Many people have bought generators or home solar and battery systems, often at great expense.

To some people, electric vehicles are a better option because they can serve multiple functions. Another big advantage: The battery in an F-150 Lightning or the electric Chevrolet Silverado pickup, which is expected to go on sale this year, can store a lot more energy than home batteries that are sometimes installed with rooftop solar panels. Pair an electric truck with a home solar system, the thinking goes, and a family could keep the lights on for days or even weeks.

The use of electric vehicles as a source of power has intrigued electric utility executives, including Pedro Pizarro, who heads the board of the Edison Electric Institute, the industry’s main trade organization, and is the chief executive of Edison International, which provides power to millions of homes and businesses in Southern California.

Mr. Pizarro’s company and other utilities are testing whether it is practical and safe to send power from electric vehicles to the grid.

By soaking up power when it’s abundant and releasing it when it is scarce, electric vehicles, he said, could serve as “a bigger rubber band to absorb the shocks and manage them day to day and week to week.”

Greater use of electric vehicles in this way should also allow utilities and homeowners to reduce planet-warming emissions by relying more on renewable sources of energy like solar and wind that provide power intermittently.

For now, few electric vehicles can provide backup power. But executives at Tesla, the dominant electric car company, and other automakers have said they are working on updates that will enable many more cars to do so.

When the power goes out in the Reigards’ neighborhood in Mount Juliet, Tenn., their truck supplies enough electricity to keep the lights on, run four refrigerators and operate a fan in a natural-gas-fueled heating system. The truck doesn’t keep their air-conditioning going, but other essentials turn on just minutes after an outage begins.

When the family lost power around Christmas, Ms. Reigard’s parents, who were visiting, were alarmed because it was freezing outside. “They started thinking, ‘My gosh, what’s going on?’” Mr. Reigard said. His response: “Nothing’s going on. We’re going to be fine.”

The couple have been so pleased by their truck that they bought 10 more for their business, Grade A Construction. They estimate that the investment is saving them $300 a month per vehicle because driving on electricity costs less per mile than burning gasoline.

While the trucks reduce operating costs, outfitting the Reigards’ home with the electrical equipment that lets it receive power from the F-150 required hiring experts and spending thousands of dollars. The couple used Qmerit, a company that manages the development, installation and maintenance of electric vehicles, storage and vehicle-to-home energy systems.

A handful of components relay information between the truck and the home’s electrical system, appliances and lights. Once set up with a homeowner’s preferences, the system decides when the truck charges its batteries and when it sends electricity back to the house.

But such systems can be complicated, and some early adopters have encountered problems.

Kevin Dyer, a software quality engineer who lives near Los Angeles, has used electric vehicles since 2009 and bought an F-150 Lightning in September. He wanted the truck to help his family ride out the rolling blackouts that have become common in California in recent years.

“We finished the installation,” Mr. Dyer said. “The truck actually powered my house. That was the high-five moment. That’s when things kind of went downhill. It just basically works, then shuts off.”

Mr. Dyer, 59, said he hoped a software update or another modest fix would solve the problem.

Energy executives said the industry was working to improve and simplify the technology to connect electric cars to homes, something they said would happen within a few years.

Oliver Phillips, chief operating officer at Qmerit, said that over time more people would be able to easily combine solar panels, home batteries and electric vehicles. Put together, those devices will “bulletproof” people against power outages, he said.

Battery-powered vehicles could eventually play an even bigger role by providing energy to the grid when demand for electricity exceeds supply, said Gus Puga, owner of Airstream Services, an electrical, heating and cooling company that worked with Qmerit to install the system at the Reigards’ home.

Some energy experts have worried that the growth of electric cars could strain grids by greatly increasing demand for energy. Mr. Puga disagrees: “I believe we’re going to add stability to the grid.”

In the auto industry, some experts have warned that frequently using cars to power homes or the grid could degrade batteries faster, reducing range — the distance that vehicles can travel on a full charge. But automakers have played down those risks.

Ford and General Motors are keen on marketing the versatility of their battery-powered models to people who have suffered power outages or fear blackouts.

“It’s really a game-changer,” said Ryan O’Gorman, a business development energy services manager at Ford. “The truck is a giant power source. E.V.s are large and can power the house for several days.”

Mark Bole, head of energy connectivity and battery solutions at G.M., said the company planned to offer a package of devices and services so customers could get the most out of their electric vehicle. “What we see as absolutely key is making it simple and affordable for the customer,” he said.

But Mr. Pizarro, the utility executive, cautioned that energy and auto companies still needed to refine the technology allowing cars to send power to homes and the grid. He expects more problems to be identified as more people start to use electric vehicles for backup power.

“It’s the early days,” Mr. Pizarro said. “There will be surprises.”