- 1). Tour your house, writing down the number of lights you have and their power in watts (W).
- 2). Refer to your manual or the information on the back of your appliances and write down their power requirements both in sleep mode and in use at the highest capacity.
- 3). Write down the number of hours you use your lights and appliances per day. For large appliances you don't use every day, write down the number of hours per week and divide by 7.
- 4). Multiply the consumption in watts by the number of hours of use for each appliance and for the lights. Add those numbers to get your average consumption per day.
- 5). Divide that number by 0.8 to account for loss in wires and in the conversion from 12 or 24v to 110 volts.
- 6). Determine your solar insulation for your area using the link in Resources. Divide the number in step 5 by the solar insulation to have the size of the PV system you need to install in your home to get 100% of your energy from solar sources.
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