One of the biggest challenges in modern solar system design is how to properly design a stand-alone solar system. Unlike a grid-tied system, a solar system with batteries consists of three separate systems all working together to create, store, and deliver energy for your electric loads. You need to ensure each component is properly sized for your specific energy needs and environmental conditions. This will explore sizing a stand-alone solar system based on an average daily load in watt hours that will be calculated from your usage habits.
For everything that uses electricity in an “off-grid” solar system, there needs to be an estimate of the average number of hours per day it will be turned on and drawing power, as well as the number of watts it will use. By multiplying watts times hours, the total amount of energy that it will need for the day is found. For an entire house, there are a lot of things drawing power at once, a lot of calculations that need to be done to determine the total load. A good way to keep track of everything in is to use the Off-grid Solar Calculator. This online tool lets you enter any number of loads into the calculation, their size in watts, and hours/day in use. It adds all of them and gives the number of watt-hours that need to be delivered every day by the system.