A professor of environmental engineering at the University of California, San Diego, says he found using thermal imaging that a building's ceiling could be 5 degrees Fahrenheit cooler during the day under solar panels that under an exposed roof.
At night, the panels help hold heat in, reducing heating costs in the winter.
"Talk about positive side-effects," Professor Jan Kleissl said.
Kleissl said his study found the amount saved on cooling the building amounted to getting a 5 percent discount on the solar panels' price over the panels' lifetime, a UCSD release reported.
The panels essentially act as roof shades, researchers said.
Rather than the sun beating down onto the roof and pushing heat through the roof and inside the ceiling, photovoltaic panels take the solar beating and shade the roof.
In a test of a building on the UCSD campus, panels reduced the amount of heat reaching the roof by about 38 percent, the researchers said.
"There are more efficient ways to passively cool buildings, such as reflective roof membranes," Kleissl said. "But, if you are considering installing solar photovoltaic, depending on your roof thermal properties, you can expect a large reduction in the amount of energy you use to cool your residence or business."