For homeowners considering the transition to solar energy, a common query arises: “How many solar panels do I need to power my home?”

The Objective

The primary aim of any solar installation should be to achieve 100% electricity offset and maximize savings. It’s not about fitting as many panels as possible on your roof. The number of panels required depends on:

  • Electricity Consumption
  • Sun exposure
  • Solar panel power rating

Manual Calculation

To get a clearer picture of how many panels you might need, follow this basic equation:

Solar panel wattage x peak sun hours x number of panels = daily electricity use

Example Calculation

Using national averages:

  1. Daily Electricity Use: According to the U.S. Energy Information Administration (EIA), the average US household in 2021 consumed 10,632 kilowatt-hours (kWh) annually. This translates to:
    • 886 kWh/month
    • ~30 kWh/day
  2. Peak Sun Hours: Divide the daily usage by the average peak sun hours for your city. For our example, we’ll use 5 peak sun hours:30 kWh/day ÷ 5 peak sun hours = 6 kW
  3. Panel Power Rating: Divide the result by the power rating of each panel. Using a common rating of 400W or 0.4 kW:6 kW ÷ 0.4 kW = 15 panels

Your Specifics

Your electricity consumption can be found on your utility bills. To determine your daily usage, divide the total monthly consumption by the number of days in the month. For a more accurate estimate, average out several months.

Peak Sun Hours

The amount of sunlight your location receives, termed as peak sun hours, plays a crucial role. A peak sun hour is when solar irradiance averages 1,000 watts per square meter or 1 kW/m^2. In the US, this varies from over 5.75 hours/day in the Southwest to less than 4 hours/day in the northern regions. To find your city’s average, Google “Peak sun hours in [your city]” or refer to a peak sun hours map.

Solar Panel Power Rating

Solar panels come with different power ratings, typically ranging from 250W to 450W. The most popular is 400W, offering a balance between output and cost. Depending on your roof space and budget, you can choose a rating that suits your needs. For this example, we’ll use 420W panels.

Final Calculation

Using the equation:

Daily electricity consumption ÷ peak sun hours ÷ panel wattage = number of solar panels

For our example:

30 kWh ÷ 5.2 peak sun hours ÷ 420W = 13.7 panels

Rounding up, you’d need 14 solar panels for a 100% electricity offset.

Need Help?

If these calculations seem daunting, we’re here to assist. Visit our FREE QUOTE or try our FREE Solar + EV Calculator. We’ll provide a tailored estimate for your home.