What does cell efficiency in solar panels mean?

[Marion Carter]

I'm shopping around for solar panels, what does "Cell efficiency" mean? I'm noticing solar panels list this.

 

[Chad Hahn]

This should give you what you want to know:

 

[smritte]

The issue with solar panels is how much usable light you have, pointed at the correct angle and how hot the panel is.

The tests are done normally in a lab which means the numbers may not be realistic in your environment. The bigger companies "normally' have the latest generation which is more efficient. The cheaper ones will normally be last generation so not as efficient. panel design also plays a big part.

A poor but simple example would be, This much light has that much energy. If your panel was 10% efficient, you only get 10% of that power from the light. 20% efficient means 20%. The reality is, as long as you stay with the newer panels, the difference is slight.

Your large heavy panels are more efficient than flexible's. A flex panel mounted on a roof will also lose efficiency due to heat where your big fixed panels, mounted an inch off the roof will cool better putting out more power.

For me, I buy good panels and buy more than I need until size becomes an issue.
My 180 watt flex panel mounted to the roof of my Teardrop, puts out less than my 140 watt fixed that I use to stand up next to my old trailer. The one on the Teardrop is a Monocrystalline and is more efficient than the fixed Poly crystal I compared it to. The heat from being mounted to the roof made all the difference.

I now know how much power I need and go higher. Last year I bought a 180 watt foldable (think low efficiency). The portability, being able to point it properly and move it out of the shade makes it better than my more efficient other three mounted panels.

So, buy more than you need and get a good charge controller. You can always add to the system.