How to Determine How Much Solar Power You Need

Solar energy is a solution for those who want to reduce their carbon footprint, save money, get tax credits and incentives, or live off the grid. Determining how much solar power a household or building needs can seem challenging. Solar panels are rated and sold in watts, but electrical consumption is usually described in kilowatt-hours. A few calculations will turn your kilowatt-hour use into a number of watts so that you can determine what size solar panel you need.

Instructions

- 1
  Find your electric bills from the past 12 months.
- 2
  Find the total kilowatt-hours (KWh) used and billed during the past 12 months. Divide that number by 12 to get your average monthly kilowatt-hour use.
- 3
  Multiply the answer in step 2 by 1,000 to derive watt-hours used in an average month.
- 4
  Divide your answer in step three by 30 for your average watt-hours per day.
- 5
  Divide the answer to step three by the average daily solar radiation in your location measured in kWh/m2/day. This information can be obtained from http://www.energysavers.gov/pdfs/208.pdf.
- 6
  Multiply the answer in step 5 by 1.2. This calculation will compensate for inefficiencies and give you the solar panel watts you need to cover your electricity consumption.

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