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The Solar Panel Requirements Calculator

Solar Panel Info

How to choose the right equipment for my needs.

Below is a compilation of information on solar panels, their usage and installation


DIY Solar Panel Book - How to make your own solar panels


Check out our new DIY solar panel handbook which shows you step by step how to make your own solar panels from scratch. Including an introduction to solar panels, inverters, batteries and charge controllers. With full color photos and videos.

Solar Panels

How to choose the right equipment for my needs.


For simplicity, let's assume you have a 100 watt device that you want to power with free solar energy for 10 hours each night.

To figure out what size solar panel, batteries, charge controller and inverter you need, follow the simple steps below.

1. Calculate how much energy is needed. 100 Watts x 10 hours = 1,000 Watt hours. That is the total energy you will need.

2. Now calculate what size solar panel you will need. Based on a ten hour day of light, the calculation is simple:
    1,000 Watt hours / 10 hours sunlight = 100 Watt solar panel.

    The reality is that most summer days give about 15 hours of sunlight and winter you get about 4-5 hours of sunlight. Always choose the worst case scenario for
    your solar panel. In this case, go with a winter day of 5 hours sunlight.
    1,000 Watt hours / 5 hours sunlight = 200 Watt solar panel.

    (Based on average United States daily sunlight hours.)

3. Calculate what size batteries you need. 1,000 Watt hours divided by 12 Volts = 83 Amp Hours of reserve battery power.
    1,000 / 12 = 83.3
    An average marine deep cycle battery will work well here. Select a larger size battery to be sure, say 100 Amp hours capacity.

4. To figure what size solar charge controller is needed, take your solar panel wattage, which is 100 watts divided by 12 Volts.
    100 / 12 = 8.3 Amps.
    Always go larger, in this case use a 10 Amp solar charge controller.

5. Calculate what size inverter is needed. That's the easy part. You need to power a 100 Watt load, so select an inverter that has
    at least 100 Watts continuous power rating.




Free online solar energy calculator.


Enter your energy requirements below and instantly see what size panel, batteries, inverter and controller you need.

(Enter whole numbers only, no letters or fractions please)

Enter total required energy needed in Watts.

Enter how many hours you need to power your device.

Enter average daylight hours for your area.


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Troy Reid


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