This detailed comparison table breaks down dimensions, wattage, efficiency, and costs to help you make informed decisions. Whether you're a homeowner, installer, or business buyer, discover how panel size impacts energy output and budget. . Solar panel efficiency is the amount of sunlight (solar irradiance) that falls on the surface of a solar panel and is converted into electricity. Most home solar panels today typically boast power ratin solar PV panel sizes by their average cost range. Keep in mind that these are the sizes and pr e a size of 2m x 1m & 1. I have to note however that the data listed in the specification sheets are normally measured at an optimum load of the module under some ideal conditions called Standard Test Conditions (STC). Solar energy generation, measured in gigawatt-hours (GWh) versus installed solar. . A solar generation calculator is an essential tool for anyone considering solar panel installation, providing estimates of how much electricity your solar system could produce based on your location, roof characteristics, and system specifications. But wattage alone doesn't tell the whole story.