PV systems 

You may have heard it said that it takes more energy to make a PV system than you get out of it over its lifetime. Fortunately, that's not even close to being accurate.

While it takes energy to make solar cells, modules and the rest of the components of a PV system, the energy payback is actually amazingly short — only 1 to 2 years. Research conducted by CrystalClear, a private company, has shown that it takes two years for a PV system with monocrystalline solar cells to make as much energy as was required to manufacture the entire PV system. Researchers also calculated the energy payback for polycrystalline cells and polycrystalline solar cells manufactured by the ribbon technique. The calculations estimated that it took 1.7 years for a polycrystalline system to reach this point and 1.5 years for modules made from ribbon polycrystalline PVs. A previous study showed that thin film modules, which require even less energy to produce, achieved energy payback in one year.

These studies were performed for sunlight conditions similar to those found in southern Europe with an average insolation of 4.7 peak sun-hours. For those who live in sunnier climates, the energy payback will be even quicker. For those who live in less sunny regions, the payback would be slower.

As it turns out, most of the energy required to make a PV system is used to produce modules — about 93 percent of the entire energy budget is devoted to making modules. As just noted, the most energy-intensive modules are those made from monocrystalline solar cells. Polycrystalline cell modules require 15 percent less energy to manufacture than monocrystalline modules. Ribbon cell module production is even more efficient. It requires 25 percent less energy than monocrystalline and about 12 percent less than polycrystalline to make a ribbon cell module. Thin film uses even less energy, about 50 percent.

"Given that a PV system will continue to produce electricity for 30 years or more, a PV system's lifetime production will far exceed the energy it took to produce it," writes Justine Sanchez in her 2008 article in Home Power entitled "PV Energy Payback."

Above: The energy a PV system will produce during its lifetime far exceeds the amount of energy it takes to produce the PV system. Photo by Dan Chiras.