What is Solar Cell Efficiency and How Is It Measured?

Posted on 01/12/2018 at 12:00 by Daniel Stieler, Phd


Solar Cell Efficiency Title Graphic


What exactly does solar cell efficiency mean?

If you’ve spent any time in the solar industry, you understand that one of the first questions out of a person’s mouth when it comes to solar technology is, “how efficient is it?”

While the measurement of solar cell efficiency is standardized and relatively easy to understand, it can often be misleading in real-world applications.

Solar cell efficiency is not comparable to the energy efficiency of your furnace or water heater. If your furnace is high-efficiency, that leads to a decrease in utility bills and more money in your pocket.

That is not what solar module efficiency is. 


The efficiency of a solar cell is the amount of power the module will produce divided by the area of the module (Watts/Square Meter).

So efficiency only comes into play when determining the area required to produce a given amount of power. Whether a module is 5% efficient or 20% efficient, if it will produce 10W, that is what you will get.

Also, efficiency is only applicable to modules that are used outdoors. This is because the sun's light spectrum is very different from indoor light sources.

For example, an amorphous silicon cell that is 6% efficient outdoors will produce more power per square meter under an LED light indoors than a 20% efficient mono-crystalline silicon module.

This happens because LED lights produce light primarily in the visible spectrum, where the amorphous silicon absorbs light to generate power.

The mono-crystalline silicon cells are higher efficiency outdoors because they convert much of the infrared light from the sun into power, but LED lights produce little infrared light.

So the next time you have a project that requires a specific amount of power, you might be surprised what technology best meets your needs.

While efficiency is undoubtedly important, it is only one aspect of what will create the best solution for you.

Do you have a project that we can help power? We would love to speak with you. 


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Categories: Solar Education