System Size Calculator
 
Step 1.  Enter your kWh usage for each month. This info should be on your utility bill(s).
(Optional) Monthly Average kWhs :  
Jan kWhs May kWhs Sep kWhs
Feb kWhs Jun kWhs Oct kWhs
Mar kWhs Jul kWhs Nov kWhs
Apr kWhs Aug kWhs Dec kWhs
Total kwh/year: kWhs

Step 2.  Select the US zone you live in and this will give you an average default kWh/year per kW. The performance of your solar panels varies depending on a number of factors including the azimuth, tilt, and shading.
US Zone:
Average kWh/year per kW:
 
Step 3.  Below is the system size required to fully cover your CURRENT utility usage. If you cannot fit this amount on your property then you can calculate what percentage of your usage you can cover with a solar power system.
System size required:

System size
Percent usage covered by solar
Panel watt size
Number of panels needed
 v 10.18.17  Rick Green