The cost of a residential solar system has come down 33% since 2008 improving financial payback1. However, have you ever asked yourself about the energy payback of the solar panels? Energy payback refers to the length of time it takes a solar system to produce, or payback, the same amount of energy required for its manufacture, transport and installation. A 2011 study2 found that it took about one year for a solar system to generate the same amount of energy required to manufacture, transport and install that solar system. Seven years earlier, in 2004, the US National Renewable Energy Lab3determined that it took three to four years for energy payback. In just seven years the energy payback is significantly faster.
We can expect the future energy payback time to be even better. For example, recent manufacturing breakthroughs could reduce the amount of pure silicon used in a solar panel by up to 90%. Creating pure silicon is an energy-intensive part of making a solar cell, so reducing the amount of silicon used results in a faster energy payback.
The energy payback calculation also depends on the location of the installed solar system. In the 2011 study, the PV system was assumed to be in a climate similar to the Midwest or East Coast. In the Bay Area a solar installation with little shade can be expected to generate about 20% more energy per year. So the energy payback for a solar system in the Bay Area would be closer to 10 months.
The useful life of a solar PV system is (more…)