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How Many Solar Panels Do I Need?

Calculate the exact number of solar panels required to offset your utility bill based on local sun hours and panel wattage.

Stop guessing if your roof is big enough for solar. Match your kWh consumption directly to panel wattage output.

Run Your Own Simulation

Adjust the inputs below. Results update instantly. No signup, no data saved — everything runs in your browser.

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Sizing Your Solar Array

Solar installers don’t size systems based on your home’s square footage—they size it purely based on your kWh consumption and your geographic sunlight exposure.

How to use this calculator

  1. Enter your average monthly electric bill.
  2. Provide your utility’s Cost per kWh (found on your bill, usually between $0.12 and $0.25).
  3. Select the peak sun hours for your region (Southwest gets more sun than the Northeast).
  4. Select the wattage of the panels you are buying (400W is the modern standard).

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Frequently Asked Questions

Our calculator automatically factors in an 80% real-world efficiency rule. Panels lose about 20% of their lab-tested output due to heat, wiring, inverter conversion, and dust.
If you plan to buy an Electric Vehicle (EV), add a hot tub, or convert a gas furnace to an electric heat pump, it is highly recommended to size your system to 120% of your current usage.

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