When light reaches a solar panel, the light energy is absorbed by the semiconductor material in the panel. This releases electrons, which can then flow in an electric current.
Solar panels produce direct current (DC) electricity. The electricity used by household lights and appliances is alternating current (AC). Inverters convert DC electricity to AC.
Four main variables affect the solar energy output from a photovoltaic panel. These are time of year, time of day, available sunlight, and panel temperature.
The formula to calculate actual solar power output is as follows: Potential Solar Power Output (based on Date and Time) x Available Sunlight x Solar Panel Temperature = Actual Solar Power Output.
It works this way: Potential solar power output is the power generated when the panel is getting the full amount of potential sunlight available at a particular time of year and time of day. This is multiplied by a percentage of available sunlight, and is then multiplied by an adjustment for solar panel temperature. The result equals the actual solar power output.
Click image above to open an interactive Flash animation that lets you set the four main variables in real time, to see how they affect energy output. The formula for actual solar power output is also displayed.
Note: Many people believe that Minnesota is not a good place for generating solar energy, because of the cold climate, and because of the angle of the sun due to how far north we are. This is a misconception. Cold is good for photovoltaic activity, and the angle of the sun here is more than adequate for good generation of photovoltaic electricity.