Build Your Own Solar Panel

The efficiency of a solar panel is determined as the ration of power out or electricity; to power in or solar irradience striking the panel.  Usually it is described as a percentage.

Think of irradience as the power of the sunlight striking a given area at a given moment.  Usually in Watts per meter squared.  Since the sun’s irradience is constantly changing due to the earths’ rotation, an average figure normally used by most manufacturers is 1000 w/m².  This will occur around noon on a clear day.

The panel’s manufacturer lists the maximum power in watts on the panel’s nameplate and from the values given, you can calculate the efficiency by dividing maximum power by 1000 times the surface area of the panel.

Example:

For a 40 watt panel with .5m² surface area, the formula would look like this..

70                                                          70
_________                                      ________
1000 x .5                 =                          500                      = .14   or  14%

Note:  Remember the 1000 used is an industry constant in reference to 1000 watts per meter square of solar irradience.

For informational purposes, solar panels are actually called solar modules in the solar industry.   Try not to get confused with all the differing terminologies used.  The field is developing rapidly and self-education is undoubtedly your best path to understanding the world of solar energy.