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  • Melissa Deaver

How Many Solar Panels Do I Need?

Typically the first question we receive with a new client is, how many panels will I need to cover my electric bill? While we could throw out a rough estimate based on size of home, the actual number of panels needed will depend upon your energy usage. No two clients are the same in their consumption, as this will depend upon lifestyle and climate.

Upon reaching out for a quote, the first thing we'll ask for is your most recent utility bill. This will provide us with a year's worth of energy usage in your home and allow us to size a system perfect to suit your needs. To take a look at this for yourself, check out a recent bill and look for the kWh consumption for each month. (To find out more about kWh, check our our blog on this here).

Once you find your kWh usage, here is a simple calculation to get a rough idea of what you'll need on your home:

Daily Usage (kWh) / Sun Hours / .9 Inefficiency Factor = Minimum Solar Array Output

Sun hours refers to how much sun you get each day where you live. This information can be found here. Inefficiency factor accounts for any circumstances that would make your system run below optimal output.

Here is an example. Let's say you live in Iowa, where you get an average of 4.5 peak sun hours a day. We'll go with the American average for consumption, which is 29.5 kWh per day.

29.5 kWh/day / 4.5 Sun Hours / .9 = 7.2839 kW Capacity System

From there, you will divide the capacity system by the energy rating of each panel. Most panels range from 370-445 watts. We'll go with a 410w panel in this example. Convert your kW number to watts (by multiplying by 1000), then we can find how many panels you'll need to cover your consumption.

7283w / 410w = 17.76 panels

Round up to 18 panels in order to cover the current usage. Keep in mind that this is a very rough estimate, and an actual estimate will require an input of several other factors. These include available roof space and which direction the space faces and obstructions at the site. All of these factors can be accounted for through our software so that we can get you an accurate quote quickly!

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