Third-party financing of solar, be it some form of lease or power purchase agreement (PPA), is becoming the leading method by which homeowners can afford to install solar. June of this year was the first month in which more Californians elected to go with a third-party-owned solar installation rather than a cash purchase, according to PV Solar Report.

This form of financing was largely non-existent in solar a decade ago, but SunEdison pioneered the process for commercial installs and firms like SunRun, Sungevity, SolarCity and, more recently, Clean Power Finance and OneRoof Energy have joined the fray with their own slant on the finance tool for residential solar.

Growth in this financing method is true for non-residential installs, as well. This chart from GTM Research shows the growth of third-party financing in non-residential CSI deployments -- 17.6 megawatts in the first quarter of 2011 up from 7 megawatts in the previous quarter.

Here's some more data out through Q2 2011, again from GTM Research's Solar Market Insight on residential third-party ownership in megawatts.

More data from GTM Research's Solar Market Insight, this on Xcel, the Colorado utility's third-party solar ownership share:

Recently, SolarCity told Greentech Media that 12,000 of their more than 15,000 solar projects completed or underway have chosen financing options. Solarcity's numbers are from across the U.S. and vary in size from residential to commercial.

SunRun and PV Solar Report released a list of the top solar cities in California for the first eight months of 2011.

The top solar cities list derives from the California Solar Initiative's (CSI) database of residential rebate reservations through the end of August 2011. In seven of these ten cities, the majority of homeowners chose a lease or PPA over a cash purchase, according to the report. The city of Lancaster led in third-party percentage at 90 percent.

Here's the list with San Jose ranked number one:

The CSI dataset uses numbers from California utilities SDG&E, PG&E and SCE.