Should I use Sanyo 200’s or Suntech 270’s? SunPower 210’s or Canadian Solar 240’s? Which size solar panel you use depends mainly on how much roof space you have available and how much electricity you plan to use (with solar power). Below are 6 steps to calculate which size solar panels you need for your building.
Step 1: Know Your Electricity Usage
Gather your old electricity bills for the past 12 months. Contact your utility company if you don’t have them and your electricity provider should gladly send you a printout with your past electricity usage. You’re looking for 2 things: (1) your monthly kW/h usage, and (2) your monthly cost.
Step 2: Know your Roof Direction
Grab a compass (maybe your car navigation, or check Google Maps) and figure out which way is South. Go outside, look at your roof and see how much roof space is facing South, Southwest, East and West. The more South the better, but West is actually okay.