Quick Answer
Guidelines for sizing off-grid solar arrays generally include determining the required DC load, calculating the total sun hours available per day, and selecting the right system size to ensure maximum efficiency and reliability.
Determine Required DC Load
To size your off-grid solar array, start by calculating your total DC load in watts. This includes the power requirements of your home’s appliances, lights, and other devices. For example, if your home uses 10 amps at 12V DC, your total DC load would be 10 amps x 12V = 120 watts.
Calculate Sun Hours Available
Next, determine the total sun hours available per day in your location. This varies by state and region, with some areas receiving as few as 4-5 sun hours per day during winter months and up to 7-8 sun hours per day during summer months. For example, states like Arizona, California, and Hawaii receive an average of 6-7 sun hours per day, while states like Maine and New Hampshire receive an average of 3-4 sun hours per day. You can use online tools or consult with a solar professional to determine the sun hours available in your specific location.
Sizing the Solar Array
To determine the required solar array size, multiply the total DC load by the number of sun hours available per day. For example, if your total DC load is 120 watts and you have 6 sun hours available per day, you would need a solar array of at least 720 watts (120 watts x 6 sun hours). However, it’s generally recommended to oversize the array by 10-20% to account for system losses and ensure maximum efficiency. In this case, you would need a solar array of at least 816-864 watts.
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