Researchers from UCSD's Jacob's School of Engineering found that the temperature of a building's ceiling was 5 degrees Fahrenheit lower right below the panels than at an exposed portion of the roof. At night, the panels held the heat and contributed to the heating cost. The scientists determined that the energy savings to heat and cool a building could amount to about a 5 percent discount off the cost of the solar panels over their lifetime.
"The panels essentially act as roof shades," said Anthony Dominguez, the graduate student lead on the project. "Rather than the sun beating down onto the roof, which causes heat to be pushed through the roof and inside the ceiling of the building, photovoltaic panels take the solar beating. Then much of the heat is removed by wind blowing between the panels and the roof."
He noted that a space between the panels and a surface help air circulation and enhance the effect, which means that tilted panels provide more cooling. For the specific building that was investigated, the research team found that the panels reduced the amount of heat reaching the roof by about 38 percent.