Quick Answer
Sizing a solar array for off-grid use requires calculating the total energy demand, accounting for peak sun hours, and selecting a suitable panel configuration.
Calculating Energy Demand
To size a solar array, calculate the total energy demand in watt-hours (Wh) using the highest monthly energy usage. For example, if the highest monthly energy usage is 1,000 kWh, convert this to watt-hours by multiplying by 1,000 (1,000 kWh x 1,000 Wh/kWh = 1,000,000 Wh). Then, divide this number by the total number of hours in the month (1,000,000 Wh / 720 hours = 1,389 Wh/hour).
Determining Peak Sun Hours
Peak sun hours (PSH) are the number of hours a solar panel receives direct sunlight. PSH varies by location, with an average of 5-6 hours per day in most regions. Use a PSH chart or consult a professional to determine the PSH for your location. For example, if the PSH is 5.5 hours per day, multiply this by 30 to get the total PSH per month (5.5 hours x 30 days = 165 hours).
Selecting a Panel Configuration
A typical solar array is sized to produce 10-20% more energy than the total demand to account for system losses. Use this margin to select a panel configuration that meets the calculated demand. For example, if the calculated demand is 1,389 Wh/hour and the desired margin is 15%, the required system size would be 1,589 Wh/hour (1,389 Wh/hour x 1.15).
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