Understanding Solar Panel Specifications Part #2: Power, Tolerance & Efficiency

In Part #1 I went into great detail about why the “Max Power” quoted on your solar panel specification sheet and the real max power you will actually get from that panel are very different numbers. I showed you how to calculate a more accurate max power by using some little known temperature specs.

In this post I’ll go through the other important numbers that you should look at when comparing solar panels.

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How To Read A Solar Panel Specification: Part #1 Power & Temperature Specs

Magnifying the NOCT on a solar panel specification

Discover how to read a solar panel specification

Does a solar panel specification with “Max Power” rated at, say 190W, really produce a maximum power of 190W when it is on your roof in the blazing sun?

Short Answer: Not on your nellie!

The max power rating (in Watts) that your solar panels are rated at is the figure that everyone quotes when talking about “panel size”. If the installer or salesperson talks aout a “190W or 250W panel” they are talking about the “max power” rating of the panels. This rating is based on the power output measured from that panel under “Standard Test Conditions” (STC) that, unfortunately, are a long way from “Real World Operating Conditions”.

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