Over 800 people across the United States took advantage of a novel online deal to get a discount setting up solar panels on their rooftops.

One of America’s top solar companies, SolarCity, partnered with the coupon website Groupon for the offer. For $1—the price of a regular cup of coffee at McDonald’s—buyers could get $400 off a solar contract that includes solar panel consulting, surveying, custom design installation and ongoing customer service. It works out to getting three to four months of free electricity.

The deal ran through June and July, and put solar on the radar for millions of online shoppers who might normally visit Groupon’s website for deals on hotels or manicures.

“The Groupon program preformed very well and the response exceeded our expectations,” said Jonathan Bass, vice president of communications for SolarCity, a California-based company chaired by Elon Musk of Tesla Motors and Paypal fame.

The deal wasn’t Groupon’s first foray into solar campaigning—but it was the largest. The discount was offered to customers in 15 states, and comes at a time of rising popularity of solar power, especially the residential version.

In 2008, there was only 78 megawatts of residential photovoltaic solar up and running, according to the trade group Solar Energy Industries Association—enough to power more than 12,000 homes.

At about the same time, SolarCity started its solar leasing plan. The program streamlined rooftop solar access to consumers, offered lower upfront costs than solar panel ownership and ultimately helped spark the rise of similar companies.

Five years later, in 2013, the number of new residential PV solar installations tracked by SEIA jumped tenfold. During that time, the national average price of solar PV systems plummeted from approximately $8 per watt in 2008 to around $3 per watt.

Today, buying solar panels can cost up to $20,000, as much as a new car. Solar leasing can drop that initial cost to zero. Leasers pay a monthly fee and surrender their renewable energy tax incentives to the solar company. In most states solar owners can get breaks on their utility bills by selling the power they don’t use to the grid.

Power companies make their money selling electricity to end users—often boosting their profits by generating the electricity at their own fossil fuel plants. They see the rise of rooftop solar and other forms of customer-produced energy, called distributed energy, as a threat because they reduce the need for power from the grid. The Arizona Public Service Company and other utilities are fighting back by trying to impose extra fees on solar users plugged into the grid.

The utilities’ concerns are not unfounded. In Germany, for example, clean energy accounts for more than a quarter of the energy supply. Distributed solar generation helped drive much of that growth—and also has contributed to the drop in utilities’ market share and historic plummet in revenues. Private individuals own about more than a third of the country’s renewables capacity, while its big four utilities make up about 5 percent.

Despite the utility-led pushback against residential solar users in the United States, SolarCity’s business is thriving. Around 70 percent of 2013’s new residential installations came from solar leasing companies; SolarCity was the top provider. Since the company went public in 2012, its stock price has jumped from $8 per share to around $74 per share today.

But was the company’s Groupon deal a success?

The deal webpage states that more than 820 people purchased the deal, a fraction of the 17,644 new customers that SolarCity signed up in the first three months of 2014. Groupon and SolarCity would not share the exact number of buyers, and declined to say where those consumers live. 

The campaign could be successful “if everybody that does the Groupon actually signs a lease,” said John Farrell, a senior researcher at Minnesota’s Institute for Local Self-Reliance, which focuses on renewable energy policy. “But there are going to be people who look at it [and it] turns out their house isn’t suitable for solar or…it just may not work out for them.”

Groupon will provide a refund to people who go through the consultation process and discover that their house can’t support solar, potentially because of roof design or too much tree shading.

The deal was a “creative way to reach people,” said Farrell. Most people who go to Groupon, he said, “probably weren’t thinking about solar energy as something they might find there.”

SolarCity teamed up with BestBuy earlier this year to make its residential solar service available at select stores.