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Solar leases have become a popular way for consumers to use solar electricity without paying for the expensive upfront price. Case in point: demand for SunPower’s (s SPWR) residential solar leases is far greater than the money available to finance them, company executives said Thursday.

“Our residential lease business remains strong, with demand outstripping our financial capacity in the first quarter,” said Tom Werner, SunPower’s CEO, during a call with analysts to discuss quarterly earnings.

The Silicon Valley company signed over 2,100 leases during the first quarter, bringing the cumulative total to over 16,200. SunPower launched the lease program in 2011. The lease sign up rate is roughly the same as in 2012, during which it signed up 11,415 of them through its network of dealers, or roughly 2,800 of them per quarter.

Homeowners who sign leases, which run 20 years, pay a monthly fee for using the solar electricity from the solar panels installed on their rooftops. They don’t own the equipment and aren’t responsible for its maintenance or repairs. SunPower raises money from investors to finance the leases. The investors, which include banks and companies such as Google, put up the money partly to take advantage of a federal tax credit that amounts to 30 percent of the price of all the solar energy system installed using their funds.

Since the lease business is fairly new, it hasn’t been making a big impact on SunPower’s financial performance though. The company’s shares shot up 17 percent after its earnings announcement mainly because it delivered better financial results than expected.

The company generated $635.4 million in revenue for the first quarter, up 29 percent from the $494.1 million for the first quarter in 2012. It narrowed its losses to $54.7 million , or $0.46 per share, from $74.5 million, or $0.67 per share, year over year.

SunPower makes solar panels and develops power plants. It’s building two huge projects in California. It has installed over 90 percent of the solar panels for the 250MW power plant called California Valley Solar Ranch, which is owned by NRG Solar. It recently started building two projects totaling 579MW that their owner, MidAmerican Solar, called Antelope Valley Solar Projects.

Internationally, SunPower continues to do well in Japan, a hot market that began offering fat incentives for solar energy generation after the Fukushima nuclear power plant disaster in March 2011. Through mostly Toshiba and a little through Sharp, SunPower’s seeing more demand for its solar panels in Japan than it had anticipated, Werner said. Sales volumes doubled from 2011 to 2012 and could double again in 2013, said Howard Wenger, the company’s head of global sales and development.

Most of the company’s solar panels are going to residential rooftops in Japan. Living space tends to be small (and more efficiently used) in Japan than it’s the case in the United States, so SunPower’s highly efficient solar panels are a good fit, its executives said. Its silicon solar panels can convert about 21 percent of the sunlight into electricity, higher than other silicon solar panels on the market today. Silicon solar panels accounted for 89 percent of the solar panels made in 2012, according to GTM Research.

SunPower has had to cut production and costs in the past two years as the global solar market saw a pricing collapse from an oversupply of solar panels.

The average wholesale prices worldwide fell 50 percent from 2011 to 2012 while demand for them grew only 5 percent during 2012, said NPD SolarBuzz. Dozens of solar panel makers around the world have filed for bankruptcy.

SunPower executives said they have beaten their cost-cutting goals.

“It’s brutal to be exclusively a module manufacturer,” Werner said. “As you look at SunPower, we moved from modules originally to systems a few years ago, and what we sell today is energy in the form of leases or PPA (power purchase agreements).”