How efficient are solar panels? How much power can they produce per square foot?
The most commonly used solar panels have efficiencies ranging from 11%-14% and produce about 10-13 watts per square foot. New panels are on the market that reach up to 20% in efficiency; however, in general, the price per watt rises significantly with increasing panel efficiency. So, although efficiencies can reach up to 30% or more, the cost is usually prohibitive except for military or space applications. At the end of the day, panel efficiency really equates to how much power can be generated in a given amount of roof space. So, for basic planning purposes, a good rule of thumb is 12 watts per square foot.
