Panel size matters mainly because it decides how much power fits on your roof. What really counts is efficiency, the share of sunlight a panel turns into electricity. A more efficient panel produces more watts from the same space, so you need fewer panels to reach your goal.
How big is a residential solar panel?
Most home panels sold today measure roughly 6 feet by 3.5 feet and produce about 430 to 470 watts. Larger commercial panels exceed 600 watts but are too big and heavy for most roofs.
What is the difference between size, wattage and efficiency?
- Size is the panel’s physical footprint.
- Wattage is its rated output under standard test conditions.
- Efficiency is how much of the sunlight hitting the panel becomes electricity. Premium residential panels now reach roughly 22% to 24%.
Two panels can be the same size with different wattages. The more efficient one simply makes more power from that footprint.
When does panel size matter most?
On smaller or more complex roofs. California fire code requires setbacks and access pathways around the array, and vents, chimneys and skylights take up more space. On those roofs, higher-efficiency panels let you fit the system you need. On large roofs and ground mounts, space is less limiting and cost per watt matters more.
Which panel does Stellar Solar recommend?
Stellar Solar installs the REC 460 Alpha Pure-RX, a 460-watt panel with efficiency up to 22.6%, a low temperature coefficient for hot afternoons and degradation of about 0.25% a year. We design each layout around your roof and your SDG&E usage.
What about the panels this article used to compare?
An earlier version of this article compared older SunPower, LG and Panasonic models. SunPower Corp. filed for bankruptcy in August 2024, and LG and Panasonic have left the solar panel business. If you already have one of those systems, Stellar Solar can still service or expand it. See what to do if your solar company goes out of business.
Get a free, no-pressure quote and we will design a system around your roof and your SDG&E usage.
