Quick Answer
To calculate the size of solar panels needed for your cabin, first determine your daily energy needs, then divide that by the number of peak sun hours your location receives per day, using the solar panel's wattage rating per hour of peak sun.
Understanding Your Energy Needs
To calculate the size of solar panels, start by determining your cabin’s daily energy needs. This includes all appliances, lighting, and other devices. A good rule of thumb is to estimate 1 kilowatt-hour (kWh) per person per day, so for a small cabin with two people, you might need 2 kWh per day. Next, calculate your cabin’s daily energy usage in watt-hours (Wh) by multiplying your daily energy needs by 1,000 (since 1 kWh = 1,000 Wh).
Calculating Peak Sun Hours
Peak sun hours (PSH) are the number of hours your location receives direct sunlight per day. This varies by location and time of year. For example, Phoenix, Arizona receives around 7 PSH per day, while Minneapolis, Minnesota receives around 4 PSH per day. To calculate the size of solar panels needed, divide your daily energy needs by the number of PSH your location receives per day.
Sizing Solar Panels
Once you have your daily energy needs and the number of PSH your location receives per day, you can size your solar panels. A common solar panel rating is 300 watts. If your cabin needs 2 kWh per day and your location receives 4 PSH per day, you would need 1,000 Wh (2 kWh) / 4 PSH = 250 watts of solar panel rating per hour of peak sun. To calculate the total number of solar panels needed, divide your daily energy needs by the solar panel rating and then by the number of PSH per day: 2 kWh / 250 W/h/PSH = 8 hours x 4 PSH = 32 solar panels.
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