Solar companies tinkering away on new technology have raised millions of dollars in venture funding. But other startups see opportunity in building, owning, and operating solar plants for customers, not in pushing the technology itself to the next level.

Solar Power Partners is one of them, and it has closed $100 million in debt and equity financing and will raise an additional $60 million by the end of this year.

The Mill Valley, California, startup uses its own source of funds to build, maintain, and operate a solar facility on a customer’s site. The customer, through a power purchase agreement, promises to buy electricity from Solar Power at agreed rates for at least 15 years. At the end of the term, the customer can purchase the system or renew the contract.

“This enables us to take advantage of the state and federal tax incentives that in most cases the customer cannot and allows us to deploy solar at the most competitive price,” said Solar Power Chief Executive Alexander Welczeck.

Buyers are able to lock in electricity costs and don’t have to commit capital up front to build the project. A 1 megawatt solar facility can cost about $7 million, said Mr. Welczeck. Solar Power typically builds solar systems that are between 0.5 and 1.5 megawatts.

The new financing will be used to expand the startup’s business nationally. To date, it has focused on California, New Jersey, Connecticut, and Hawaii. The company has already built 19 projects and is working on 22 others. By the end of the year it will have 15 megawatts of installed capacity.

Solar Power’s customers include grocery stores such as Safeway and such universities as University of California at San Diego. The company also works with municipal customers and airports.

The announcement highlights the shift of power purchase agreements as the dominant model for the delivery of solar systems. It also is an indication that utility regulators increasingly are easing their restrictions on customers choosing to purchase electricity from other sources than the grid.

“It is the predominant way that solar projects will be managed in the future,” said Paul Karayan, an analyst with Lux Research.

MMA Renewable Ventures, Recurrent Energy, and SunEdison are three other companies that see promise in building, owning, and operating solar facilities.

But it is a difficult market to succeed in, said John Quealy, analyst with Canaccord Adams.

“You have to have very good access to capital because cash flow is not positive for several years,” he said. “You also have to have enough expertise to run a power plant.”

Solar Power’s investors and lenders include: United Commercial Bank, Globespan Capital Partners, The Enlightened World Foundation, Carrelton Asset Management, Dry Creek Ventures, Silicon Valley Technology Group, and Energy Investors Funds. The startup previously raised $6.2 million in a first round of venture funding.