Clean Energy Payback

Photo of Hawaii's Mauna Lani Bay Hotel and the PV system installed on the roof.

Hawaii's Mauna Lani Bay Hotel had acres of roof space, making it the perfect host for a PV system. The hotel's owners displayed their environmental stripes and saved a substantial sum of money by working with PowerLight Corporation to install a PowerGuard^® system of insulating PV roofing tiles. The system covers 10,000 square feet and generates 75 net kilowatts of electricity. It will reduce the hotel's utility bills enough to pay for itself in five years.

We have to use energy to manufacture and produce PV systems. But since that energy can come from either environmentally friendly or unfriendly sources, environmental impacts are difficult to quantify. To avoid that uncertainty, PV experts prefer to evaluate the "energy payback" of PV systems, that is, how long it takes a PV system to generate enough zero-emission energy to offset the energy used to produce it.

Studies have shown that, depending on the type of PV technology, the clean energy payback of a PV system ranges from one to four years. With life expectancies of 30 years, 87% to 97% of the energy produced by PV systems will be free of pollution and greenhouse gas emissions. For more information, see the NREL report, "Energy Payback: Clean Energy from PV" (PDF 75 KB). Download Adobe Reader.

In other sources, a Dutch report from Utrecht University, places the energy payback at 1.3 to 4.6 years, and a report by Energy & Environmental Economics, Inc., and Siemens Solar Industries published in Home Power Magazine found energy paybacks ranging from 1.8 to 4.1 years (PDF 132 KB). Download Adobe Reader. Additional papers on the PV energy payback are available on the Ecotopia Web site.