Decade-old startup d.light has sold solar-powered lanterns and lights to millions of customers in off-grid rural areas like Sub-Saharan Africa.

But now the company, founded by two Stanford entrepreneurs, is shifting its focus to grow its business of selling larger, more powerful solar panels and solar-powered gear like radios and fans. Their complete home solar product can hold its own against a traditional power grid connection and a local electronics store, but for a fraction of the cost.

D.light CEO and co-founder Ned Tozun, who spoke to Fortune on the phone from Nairobi, says that’s the entire point. “We think solar will leapfrog the electric grid, like cell phones have leapfrogged landlines in Africa and Southeast Asia,” he says.

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On Wednesday morning, d.light announced that it had raised another round of $22.5 million in funding to grow its home solar business. About $15 million of that was in the form of equity from investors that specialize in energy investments in the developing world, including KawiSafi Ventures Fund and Energy Access Ventures.

Longtime investor Omidyar Network was also involved, as was NewQuest Capital Partners. In addition, $5 million of the round was a grant from the Shell Foundation, the U.S. Agency for International Development (USAID) and its Development Innovation Ventures, and the United Nations Capital Development Fund.

D.light has sold about 250,000 of these complete home solar systems. About half of its customers bought those systems using loans from micro-financing groups, and the other half are using d.light’s pay-as-you-go cell-phone-based payment system. Previously, d.light had partnered with a company called M-KOPA and was using M-KOPA’s payment system, but now d.light has developed its own service.

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Clearly, these pay-as-you-go complete home solar systems are starting to provide good business. M-KOPA itself, which was founded by one of the original creators of the wildly successful mobile payment system M-Pesa, recently raised $19 million. That round was led by Generation Investment Management, a London-based fund started by investors David Blood and former Vice President Al Gore, and also included Virgin’s Richard Branson and Steve Case, founder of AOL.

Two other startups that are also using the cell-phone-based pay-as-you go solar model are Off Grid Electric and Azuri Technologies. Off Grid Electric has raised $25 million from DBL Partners, a fund that backed Tesla TSLA and SolarCity SCTY , as well as SolarCity itself, and Vulcan Capital, the fund of Microsoft co-founder Paul Allen.

See also: SunPower Embraces Drones and Robots to Help Evolve Its Solar Farms

The market might sound crowded already, but it’s actually just the beginning. There’s room for many companies.

While d.light has more recently focused on their complete home solar product, the company has a decade of experience selling its well-designed and ultra-cheap solar lanterns. The company has managed to sell enough of those to impact 65 million people, many of whom are families and school children that use the lights to read at night.

At the rate d.light is growing—the company now has more than 500 full-time employees—Tozun says it will be able to sell enough solar products, both home systems and lanterns, to impact 100 million people by 2018.