Energy conversion efficiency is an expression of the amount of energy produced in proportion to the amount of energy consumed, or available to a device. The sun produces a lot of energy in a wide light spectrum, but we have so far learned to capture only small portions of that spectrum and convert them to electricity using photovoltaics. Today's crystalline solar panels are about 7% to 18% efficient. For comparison, a typical fossil fuel generator has an efficiency of about 28%. Most solar panels lose a little efficiency each year upon prolonged exposure to sunlight. The efficiency loss per year depends on manufacturer, this is the importance of purchasing higher quality panels to ensure your efficiency is maintained as much as possible over the life of your Solar PV system and you are generating as much electricity as possible. Research and development are working on ways to convert more of the energy in sunlight to usable energy and increase the efficiency of PV systems. Some experimental PV cells now convert nearly 40% of the energy in light to electricity.
