This should only be less than 100% if you'll be getting some of your electricity from a separate source (wind, hydro, geothermal, etc.)
List your appliances and their power consumption in the calculator below. It's important to include every appliance in every room of your home, and light bulbs too (you may find it's easiest to add up all your light bulbs' wattages on paper first and include them as one item in the calculator). If it's on a switch or plugged into an outlet, list it.
Use the map to the right of this form to find this answer (1 kWh/square-meter/day = 1 hour of sun/day).
Choose the highest AC voltage you'll need.
Refer back to your appliances list from Part 3 and consider which appliances could be running at the same time. Add up the "Average Watt-hours per day" numbers from those appliances.
Choose the highest DC voltage you'll need.