What is Panel Efficiency?

Panel efficiency, or solar cell efficiency, is a way to measure the performance of a solar panel. It describes the  ratio of available energy from the sun that is converted into usable electricity by the solar panel. 


In other words, if 100 units of energy hit the panel's surface in the form of sunlight, and the panel produces 20 units of energy in the form of electricity, the panel has an efficiency of 20%. If 100 units of energy hit the panel's surface in the form of sunlight, and the panel converts 17 units into usable electricity, the panel's efficiency is 17%.


How Should Efficiency Factor into My Equipment Choice?

Although some labs are working on experimental panels that could be up to 45% efficient, most residential panels currently on the market top out at around 18-21% efficiency, including the tier-1, black-on-black panels that Project Solar uses. 


Higher-efficiency panels are good because they allow more energy to be produced in a smaller space. However, paying more for slightly higher-efficiency panels usually doesn't make sense unless they allow you to fit more panels on your roof, so if a sales rep tries to justify higher prices with a few extra percentage points of efficiency, they might not have your best interest in mind.

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