Installers who sell high-efficiency panels love to flaunt that point when selling their system. But in most cases, panel efficiency doesn’t count for much, except higher prices. Having the highest efficiency panels on the market does not mean your system is producing the most. The watts of a system will be the single largest determinant of system production, not efficiency.
The straightforward definition of panel efficiency is the percentage of solar energy that is converted into electrical energy. To give an example of this, the average dimensions of a residential solar panel is 3.5ft. X 5ft.; this panel may produce anywhere from 250 watts to 345 watts. The difference in watts is determined by the efficiency of the panel. Today, residential panel efficiency tops out at about 22% (345 watt panel) and it bottoms out around 15% (250 watt panel). Approximately 95% of the panels on the market will fall in this range.
Reasons to get high-efficiency panels: If you have limited roof-space or limited optimal roof-space, and you cannot fit as many watts on your roof as you would like, then it may make sense to pay more for the higher-efficiency panels. Other than that, you’re just paying more for the sake of paying more.
Reasons to get lower-efficiency panels: They will save you a whole lot more than paying the high price of the latest technology. If you are buying a new pair of skis or a new car, you get technological improvements you can enjoy. With solar panels, they all produce the same thing – kilowatt-hours of electricity (kWhs). Lower-efficiency panels will produce the same kWhs as high-efficiency panels, but they’ll take up a bit more space to do it.
Exceptions: There are all sorts of other considerations when choosing panels. Sunpower’s extremely high-efficient panels offer the industry leading warranty, Solarworld panels boast that they’re American Made, and LG has some serious brand recognition. All those factors may play into your decision of what panels you want, but don’t let the efficiency play a major role if you have the roof-space – otherwise you’re just giving money away.