Solar panel efficiency is simple, but there a few things you need to understand.
There are 3 main types of solar efficiency.
1. Module Efficiency
2. Area Efficiency (Density)
3. Cell Efficiency
1. Module efficiency measures how well a solar module (aka panel) converts the Sun’s energy into usable energy. If the Sun dumps 100 Watts of energy onto the module and the module spits out 15 Watts, the the module is said to have 15% module efficiency (15 W / 100 W = 0.15 = 15%). If you want to brag to your friends that you have a top tier efficiency panel, care about this.