My prospective supplier states that the Schuco 210 wattSMAU-1 panel has a cell efficiency of 16.8%, whereas yourtable gives a panel efficiency of 12.43%. What is the differencebetween panel and cell efficiency and which should be my guide?

Great question.

Cell efficiency is measured as the percentage output of energy to the theoretical amount of energy supplied by the Sun (hitting the cell). So if 100 Watts hits the cell (under Standard Testing Conditions, STC,which is laboratory conditions), and it spits out 16.8 Watts, then thecell efficiency is 16.8%.

My table gives panel efficiency of how much output of energy (asmeasured by PTC, which is the realistic test conditions of a panel on aroof) to the amount of space that panel takes up in squarefoot area.

Your supplier is right, but if you want a point of comparison, askhim to give you the “cell efficiency” of all the competitor’s panels.What my table allows you to do, is compare all the panels (eligible forrebates in CA, which is more than 1,700) by the panel efficiency. Though our efficiency measurements are slightly different, mine arestandardized across all panels using the data that CSI (CaliforniaSolar Initiative) uses to pay rebates. So, you can easily see howSchuco 210’s compare to any other 210 panels (or 200, or 220, etc…)

Hope that answers your question. He’s not lying. I’m just giving youmore information.

Image: Confusing chart of solar cell efficiencies

Source