Use the calculator below to size your system: Estimate your array size, panel count, battery capacity, controller current, and inverter size. Adjust defaults to fit your setup. Tip: Find yours via NREL PVWatts, then paste it here. Accounts for wiring, controller & inverter losses. Notes: Array W = (daily kWh ÷ sun hours ÷ efficiency) × 1000.
If the amount of sunlight drops significantly during the winter months, then you should size your solar panels based on the least amount of sunlight available during the year. If the available sunlight drops by half to 2.5 hours a day during the winter, then we would double the size of our PV array to 10 panels.
This will decide everything about your PV setup, from the inverter down to the solar panels you buy. Small systems, such as those on an RV or boat, should use 12V systems, while larger solar arrays do best with 24V. A good rule of thumb is that if your energy needs are less than 1,000 watts, go for a 12V system.
Since we have 24V batteries, we also want 24V solar panels. The amp output of a 24V 250-watt solar panel will be 10.4A. This is under ideal conditions, as variation in sunlight will affect the power output, and the amp output, of our solar panels. When wiring solar panels, you can choose to wire either in series or parallel.
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