How Many Solar Panels Do I Need?

Three simple steps to calculate how many solar panels you need.

Step 1: Determine your solar array size in kW and enter it into the calculator below.

Step 2: Decide which solar panels you want to use, and enter the DC Watt rating of the specific solar panel model you want to use into the calculator below.

  • Example: Suntech STP210-18/Ub-1 are rated at 210 DC Watts.  Sunpower 230-WHT are rated 230 DC Watts.

Step 3: Calculate!

  • Formula: Number of Panels = (Array Size in kW * 1,000 W/kW) / Solar Panel DC Watt rating.

Hint: Now you’re wondering how much roof space that many panels will need.  Well a general estimate is 17-20 sqft per panel.  So if you need 20 panels, you’ll need 340-400 sqft of unobstructed (mostly South-facing) roof space.