Solar Calculator Estimates Solar Electricity Production & Payback Time

If you’re interested in the prospect of moving toward getting a home solar system, but don’t know enough details yet about the potential electricity production that a solar array could provide to your own house, or about the basic economics of solar electricity in your region, to want to get a free solar site evaluation and estimate, this solar calculator might help.


The PVWatts solar calculator, from the National Renewable Energy Laboratory (NREL), takes a few basic inputs from the potential solar homeowner, starting with its geographical location (anywhere in the US), and then offers a number of variables, such as the local retail price of electricity, the roof pitch, the desired size of the system, etc., for the user to specify.

The web application then calculates the estimated annual and monthly solar electricity production, as well as the estimated dollar value of that energy, according to the most recent data, so potential solar users can get a quick overview of the numbers to see what a solar PV system will do for them.

The solar calculator, which was just updated in September 2014 to more accurately predict current solar performance, also allows users to change the default basic inputs at will to calculate different scenarios, such as a larger array, or using a different solar technology or mounting system, tilt angle, etc., to compare the options.

The PVWatts calculator also automatically lists the solar incentives available for the solar PV system, based on the type (commercial or residential), and the location, and users can enable them on their solar calculation if applicable to them. The calculations use an installed cost of solar of $3.70/Wdc, which includes all hardware, labor, and other costs, and assumes that the installation cost is financed with a 25-year, 7.5% interest rate loan.

While this solar calculator is a handy way to get the basic cost of solar for your home or business, as well as to estimate how much electricity (in kWh AC, the same metric used on your utility bill), and how much that electricity would cost (its energy value in dollars), monthly over month as well as annually, it’s no substitute for talking to a solar expert about the details. Additionally, specific details may vary based on the loan, the price of electricity, and a number of other factors, so don’t use the numbers there as the final word on your situation without getting a site evaluation.

Find out more about how you can go solar!

Solar 101

February 19, 2015

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