When Terrence Dwyer received a knock on his door and a flyer for a solar panel system small enough to fit on his deck, he was quickly sold. Solar systems that plug into regular wall outlets have been popular in Europe for years and are gaining traction in the United States for their affordability and simple installation.

“We thought absolutely, let’s do this right away,” said Dwyer, who lives in Oakland, Calif.

The small-scale solar systems could become attractive to more homeowners now that President Donald Trump’s sweeping budget-and-policy package will scrap residential rooftop solar tax credits and may shift interest to cheaper alternatives. Even before the GOP bill passed, manufacturers of the smaller systems known as plug-in or balcony solar were seeing increased demand and other positive signs, such as a new Utah law streamlining regulations for homeowners to buy and install them. The systems about the size of a door haven’t been as widely adopted in the United States as in Europe because of a lack of awareness, patchwork utility rules and limited availability.

The $2,000 plug-in solar system installed on Dwyer’s backyard deck in March consists of two 400 watt panels, an inverter, a smart meter and a circuit breaker. It saves him around $35 per month on his power bill because he is consuming less energy from the grid, but he said reducing his carbon footprint was his primary motivation.

Had Dwyer opted for rooftop solar, he would have paid $20,000 for the system and $30,000 to upgrade his roof to support the panels.

Dwyer bought his system from Bright Saver, a nonprofit company in California that advocates for plug-in solar. In addition to the type Dwyer bought, the company also offers a smaller model costing $399 that recently sold out in six days.

“The interest and demand have been overwhelming,” said Cora Stryker, a founder of Bright Saver. “It is clear that we are hitting a nerve — many Americans have wanted solar for a long time but have not had an option that is feasible and affordable for them until now.”

Some questions remain about how much customers could save. Severin Borenstein, a professor at the University of California, Berkeley’s Haas School of Business, said the cost of some portable solar systems in the United States would make it hard for customers to come out ahead on their utility bills over the time they own them. He estimates the price of a $2,000 system in the United States works out to paying about 20 cents a kilowatt-hour over a 25-year period, which only saves people money if they have high utility costs. By comparison, Borenstein said the cost of systems sold in Europe, typically around $600, is equivalent to paying about 5 cents to 6 cents per kilowatt-hour over 25 years.

Other companies selling plug-in solar kits include Texas-based Craftstrom. It has sold about 2,000 systems in the United States since 2021, mostly in California, Texas and Florida. The company’s basic kits contain a solar panel that can fit in a backyard or other sunny space, along with equipment to maintain and regulate the flow of energy, including an inverter and smart meter.