Solar panels collect sunlight and convert it into electrical energy in the form of DC power, but there are different operating voltages and types of solar panels. Solar panels are either mono-crystalline or poly-crystalline and each has their own merit. The mono-crystalline panel has traditionally been considered as the more efficient of the two, however, it is far more important to locate a reliable manufacturer than to focus on the difference between the two. Renogy produces a very reliable solar panel. A typical solar panel efficency is from 12-20%.