Solar panels are seen on the rooftop of a house near the sea in Santa Cruz de Tenerife.
Solar pv panels could provide cheap air-conditioning for homeowners.

There are numerous benefits to installing solar panels - good karma notwithstanding - long-term savings on energy bills, tax incentives and a clean, renewable energy source are the primary benefits.

But solar panels can also provide a cheap form of air conditioning for homeowners, according to a team of researchers led by Jan Kleissl, a professor of environmental engineering at the UC San Diego Jacobs School of Engineering.

The study, which appears in the current issue of the journal Solar Energy, found that a building's ceiling was 5 degrees Fahrenheit cooler under solar panels than under an exposed roof. In addition, the panels retained the heat during the night, reducing heating costs in the winter.

"Talk about positive side-effects," said Kleissl.

Researchers used thermal infrared cameras to record the temperature of the Powell Structural Systems Laboratory, which is partially covered by solar photovoltaic (PV) panels. Although the results are site-specific Kleissl said he is confident the research provides a model that can be extrapolated.

"There are more efficient ways to passively cool buildings, such as reflective roof membranes," he said. "But, if you are considering installing solar can expect a large reduction in the amount of energy you use to cool your residence or business."

The study determined that the amount homeowners saved on cooling the building amounted to receiving a 5 per cent discount on the solar panels' price, over the panels' lifetime.

"It's mostly that shadow effect, like when you park your car under a tree. The sun hits the solar panels, not your roof," said Kleissl.

"It's very intuitive, like having a blanket. In winter, the solar panels won't allow all the heat to be lost to the atmosphere."