The New York Times' Lisa Prevost takes a look at a new Department of Energy study that finds buyers will pay more for homes with solar panels.

The research looked at sales data on nearly 23,000 homes--4,000 of which had solar photovoltaic systems--in eight states from 2002 to 2013. The takeaway: buyers will pay a $15,000 premium for a home with an "average-size solar photovoltaic system (3.6 kilowatts, or 3,600 watts), compared with a similar home without one. Put another way, that translates to about four additional dollars per watt of solar power"

While the data points are interesting in their own right, the research may have its biggest effect on the appraisal and mortgage industries, which have struggled for years to account for the value of green building techniques.

Arthur Wilson, a builder developing five homes (all presold) with geothermal and solar panels in Middle Island on Long Island, has had his own issues with lenders. He said that an appraisal of $498,000 for the second house to be completed was recently “shot down” as too high by bank reviewers who he said were untrained in valuing green home features.

“Any new item or feature is always a nightmare in appraising,” said Gerard O’Connor, an appraiser in Lindenhurst, on Long Island ...