Google is having a big week on the renewable energy front and, in related news, lease financing for new solar installations is rolling along.

The Internet giant with tentacles into so many things green and innovative followed its Earth Day announcement of a massive wind energy buy in Iowa with word on Wednesday that it would pony up $100 million to help finance SunPower residential rooftop solar installations. SunPower, a manufacturer and installer, itself is pumping $150 million into the quarter-billion-dollar lease finance fund.

Solar leases can be attractive to homeowners by offering low upfront costs and cheaper-than-utility electricity prices, and to investors for the lucrative tax credits they can yield. Such “third-party ownership” programs have been a driving force behind the growth in solar power in the past several years. In California, the nation’s biggest solar market, leasing went from less than 10% of new solar systems in 2007 to more than 75% in 2012, according to a study by the Climate Policy Institute, even as total new system installations rose dramatically.

Installer SolarCity has used third-party ownership programs to climb to the top of the residential solar heap. SunPower launched leases in 2011 and claimed 20,000 U.S. homes onboard as of the beginning of this year, but the company, best known for pricier but higher-efficiency modules and its utility-scale projects, has faced some challenges with leasing.

In a February earnings call, SunPower admitted that “in the middle of 2013 we were financed constrained to an extent” on solar leasing. But with a new $220 million program with Bank of America Merrill Lynch in hand, SunPower CFO Charles Boynton predicted that SunPower’s residential leasing would grow “at least 50%” in fiscal 2015.

Now comes the Google deal, which, in addition to benefiting SunPower, could be seen as recognition of solar leasing’s staying power as solar financing continues to evolve.

There was chatter last year that with system prices falling, loans might challenge leases as a finance mechanism. SunPower’s Boynton said that “we don’t lead with lease, we lead with our product,” and then consult with the customer on how to pay for it, whether it’s purchase, lease or loan.

At last week’s Greentech Media Solar Summit, a residential-trends panel had the consensus view that “loans will fill an important niche but will not overtake third-party ownership,” according to PV Solar Report. Also, Mercom Capital said earlier this month that there was a “continued upward trend in third-party residential and commercial solar lease fundraising in Q1 2014, tracking more than $1 billion raised.”

Google, for its part, had already been a big player in the growth of third-party ownership of solar, but it had been awhile since it made a play – in 2011 the company invested $280 million into a SolarCity fund and $75 million into a fund with Clean Power Finance. Overall, the hookup with SunPower was Google’s 16th renewable energy investment, with the total tab now well over $1 billion.