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This solar panel calculator estimates how many watts of panels you need to fully recharge your battery bank in a single day of sunlight. It's the natural next step after sizing your battery: once you know your storage capacity, you need enough panels to refill it before the next night.
It works by converting your battery's amp-hours and system voltage into watt-hours, dividing by your peak sun hours, then adding a 10% loss factor. In the Philippines, peak sun hours typically run 4–5 per day, though this varies with weather, season, and shading. The loss factor covers real-world inefficiencies — panel heat, dust, wiring drop, and charge-controller losses — so the recommended wattage actually refills the battery rather than falling short on cloudy days.
Use this when you already know your battery size and want to know the panel array that keeps it charged. If you're sizing from scratch, the full solar calculator handles panels, battery, inverter, and wiring together.
Common questions about sizing a solar panel array.
Convert battery amp-hours to watt-hours (Ah × system voltage), divide by your peak sun hours, then add about 10% for losses. For example, a 200Ah 12V battery (2,400Wh) over 4.5 sun hours needs roughly (2400 ÷ 4.5) × 1.1 ≈ 590W of panels — about two 300W panels.
Peak sun hours measure how many hours per day deliver full-strength sunlight (1,000 W/m²). Most of the Philippines averages 4–5 peak sun hours, lower in the rainy season. The calculator lets you adjust this to match your location.
Panels rarely hit their rated output in real conditions because of heat, dust, shading, wiring voltage drop, and charge-controller losses. The 10% buffer ensures the recommended wattage genuinely recharges your battery within the day.
That depends on charge current and battery state of charge. Use the Battery Charge Time calculator to estimate the hours needed from a given charging amperage.
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