How to calculate how much PV you need to cover your electrical needs
- Determine your energy use - you can do this by collecting a year's worth of electric bills and adding up the energy (measured in kW-hrs) used. Another way to do this is to do a plug load analysis of all of your electric devices.
- Determine the solar insolation in your region to determine kW-hrs/kW installed of PV.
- Divide one by two to get your number of installed Watts.
- Lets say you are average. The average annual electricity use per household is 10,654 kW-hrs/year (Energy Information Administration, 2005).
- From the solar resource map go here or here. If we assume you live in Kingston you can expect at least 1200 kW-hrs/kW (more if you are using thin film PV).
- 10,654/1200 = 8.9 kW. This is actually a pretty big system -- which shows you just how wasteful most people are with energy.
Before you consider installing any type of photovoltaic you should first work to optimize your home's energy efficiency.
 Things You will Need
For a plug load analysis you will need a watt meter.
 Related How-Tos
 Sources and Citations
Energy Information Administration (EIA). 2005. U.S. Household Electricity Report. Release date: July 14, 2005 at