How to Size a Solar Array

How to Size a Solar Array

Electricity (kWh) usage history on utility bill.

You, too, can size your solar array in just two easy steps! (Well, okay, there's a little research involved, too.)

To estimate the size of your solar array, you'll need to know:

1. The number of Watt-hours (Wh) you plan to produce in one day.
2. The insolation value at your location.

Watt-hours

A Watt-hour is a measure of energy. Identifying your Watt-hours goal is the most crucial part of accurately estimating how big a system--or we might say, how many Watts of solar panel generating capacity--you will need. If you plan to tie your solar array directly to the utility grid to offset your costs, start by looking at your electric utility bill for the kilowatt-hours (abbreviated "kWh") you use in one month. Since your electricity usage probably changes throughout the year, you might want to calculate your average monthly usage from the historical information found on most bills these days. People often choose to offset a certain portion of their average electricity usage based on their budget.

We strongly recommend completing a detailed Loads List.

If, however, you will not be connected to the utility grid and you will in fact be producing all your own electricity, the Watt-hours or kWh number becomes even more important. For any off-grid cabin, home, office or project, we strongly recommend completing a detailed Loads List (Power, Energy and the Loads List). If you have the patience to live off-grid, then you definitely have the patience to complete a loads list! If you don't know how many Watt-hours you are trying to produce, stop here! Do not pass Go! There is very little estimating you can do without that basic building block.