The idea that making a house more energy efficient, with or without solar panels, increases its value has been floating around in the anecdotal atmosphere for a while. Now researchers at the Ernest Orlando Lawrence Berkeley National Laboratory in Berkeley have applied a small phalanx of figures and formulas to the issue and come up with good news for home owners and solar installers.

The researchers — Ben Hoen, Ryan Wiser, Peter Cappers and Mark Thayer — have produced a report thick with statistical jargon and formulas, but they do have a clear conclusion –

“California homes with PV (photovoltaic solar) systems have sold for a premium over comparable homes without PV systems,” “The effects range, on average, from approximately $3.9 to $6.4 per installed watt (DC) of PV, with most coalescing near $5.5/watt, which corresponds to a home sales price premium of approximately $17,000 for a relatively new 3,100 watt PV system (the averge size of PV systems in the study). These average sales price premiums appear to be comparable to the investment that homeowners have made to install PV systems in California, which from 2001 through 2009 averaged approximately $5/watt (DC), and homeowners with PV also benefit from electricity cost savings after PV system installation and prior to home sale.”

These findings come from an analysis of California home sales from 2000 to 2009, comparing sales of both existing and new homes with and without solar panels. If you read the actual report, you will find out how they filtered the data to make sure they were using comparable properties and the calculations they used — it looks pretty rigorous.

Some of the home sale data did come from Riverside, but as far as solar home sales, we came in with only 87 used in the study, versus 4,262 non-solar sales, compared to higher sales areas. Sacramento led the pack on solar home sales with 483 solar home sales versus 10,928 nonsolar.