You may have heard of, or seen, solar panel efficiency advertised by module(panel) manufacturers. Here, I will explain its meaning and how the value comes about.
Solar panel efficiency is expressed as a percentage (%) and relates to how much energy is converted when light from the sun reaches solar panels.
The sun creates light energy, which when exposed to PV (photo voltaic) cells is converted to DC (direct current) energy. When this conversion occurs, energy is lost in the process.
Light energy from the sun, at peak, creates 1,000 watts of power per m2. Most LAM (large area module) panels, the like of which most residential & commercial panels are, measure approx 1.65 – 1.7m high & 1m wide, so approx 1.65 – 1.7 m2.
So, light energy created equals approx 1,700w of energy on the solar panel (1.7kw). If say, a panels efficiency (the rate at which it converts) is 19.9% then the panel produces (at peak) 338w. This is the measurement in which most panels are marketed.