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    Solar Panel Calculator

    Calculate how many solar panels you need with this free online solar panel calculator. Get system size, annual output, roof area, savings and payback.

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    What next?

    Found it useful? Share Solar Panel Calculator

    Free, no sign-up, works in the browser — send it to a friend or add it to your site.

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    How to use Solar Panel Calculator

    1. 1Enter your monthly electricity usage in kWh, or your monthly bill and price per kWh
    2. 2Pick your region or enter peak sun hours, panel wattage and system losses
    3. 3Read the number of panels, system size, annual production, savings and payback period

    Frequently asked questions

    How many solar panels do I need for 900 kWh a month?▾

    With 4.5 peak sun hours, 400 W panels and 14% system losses, you need about 7.6 kW of solar, or 20 panels, producing roughly 11,300 kWh a year.

    What are peak sun hours?▾

    Peak sun hours are the number of hours per day the sun delivers 1,000 W per square metre. They range from about 3 in cloudy northern regions to 6 or more in deserts.

    How long does it take for solar panels to pay for themselves?▾

    Divide the system cost by your yearly savings. An 8 kW system at $2.75 per watt costs $22,000; saving $1,728 a year, it pays back in about 12.7 years before incentives.

    Embed Solar Panel Calculator on your website▾

    Paste this snippet into your page. The embedded tool runs in your visitor's browser and shows a small “Powered by clkr.work” link.