Off-Grid Energy System Size Calculator
1. How much electricity do you use each month?
Look at your electric bills from the past 6 months (or less) and find the average number of Kilowatt Hours (KwH) per month. Put this number in the space to the right.
2. What percentage of your house/business power do you want to generate with solar power? If you want to produce 100% of your electricity, put 100. %
3. How many Peak Sun Hours do you get per day? Look at the Solar Map below to find this number. Hours
Minimum System Size:

Divide the Minimum System Size watts by the wattage of the solar panel you are looking at. For example, it would take 24 Mitsubishi 125-watt solar panels to produce 3000 watts..... 3000 divided by 130 = 23+ solar panels.

solar insolation map
solar insolation zone 5 Zone 5 solar insolation zone 6 solar insolation zone 4 solar insolation zone two

Zone 1      6    hours
Zone 2      5.5 hours
Zone 3      5    hours
Zone 4      4.5 hours
Zone 5      4.2 hours
Zone 6      3.5 hours

The hourly figure indicates the average (over the course of the year) amount of insolation (full sun hours) for these zones. These figures are based on the yearly average; consequently, systems based on these figures will provide more power in summer and less in winter. Winter figures for daily solar gain may be from 25% to 50% LESS than these average figures.