Formula to Estimate How Many Solar Panels You Need

If you are interested in solar energy and are wondering whether or not you can


afford to install a solar electric (or photovoltaic, PV) system in your home, you

will need to know how many solar panels it will take to deliver the electricity you

need. The reality is that there are several variables that affect the size of the

solar electric system you will need. Each system has site-specific requirements,

and there is no one-size-fits-all answer. It is much more complicated than it

seems, especially if you are planning a system that will provide 100 percent of

your electrical energy needs.

But if you have just started your exploration into the possibilities of adding solar

panels to your home, you probably would like to have at least a ballpark

estimate of how many panels your project would need. So here is a way to

calculate a very rough estimate (emphasis on "very rough") of the wattage that

your solar array will need to deliver using a few basic numbers.

Formula to Estimate How Many Solar Panels

This is a basic and rough formula you can use to estimate the number of solar

panels your house would need, based on your family's history of energy

consumption. Detailed explanations follow, and there is a blank worksheet you

can print out at the end of this report:

Formula to Estimate How Many Solar Panels

Your Solar Electric System Will Need

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1 Average daily kilowatts of electricity used (from utility bills)

2 Multiply by 1000 (kilowatts x 1000 = watts)

3 Multiply by percentage to be provided by solar

4 Divide by solar insolation value

5 Multiply by 120% (to allow for normal energy loss within system)

6 Divide by solar panel peak wattage (per manufacturer)

7 Equals Number of solar panels needed (round up to next whole Number)


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