The efficiency of a solar panel is its ability to convert solar energy into power. A panel that has an efficiency of 15% converts 15% of the solar energy that falls on it into power.
There is a great deal of hype about how efficient one panel is over another. What efficiency translates into in real terms is how many square feet does it take to generate a certain amount of power, the more efficient the panel the less space they take up. If you have limited roof area then a more efficient panel will allow you to put more kW’s on your roof and may be more cost effective.
The downside though, is that the more efficient a panel is, the more it will cost per watt. It may be possible to buy 30% efficient panels but they will cost twice as much as 17% panels and therefore will not make sense for most people. On the other hand if we use panels that are too inefficient like thin film, our mounting costs are going to be more expensive since we will be mounting twice as many square feet of panels.
Panel efficiency is just one of many factors that go into delivering a system that is optimized for the maximum ROI (return on investment), which is always our goal.