Daily Wh = Panel watts × Peak sun hours × System efficiency Example: 400W × 4. 8 ≈ 1,440Wh/day Use peak sun hours for your location (not daylight hours). Pair this estimate with your daily load plan when sizing batteries. Increasing panel count or choosing higher wattage. This solar panel output calculator helps you determine exactly how many watts and kilowatt-hours your solar panel system will generate daily, monthly, and annually based on panel specifications, quantity, peak sun hours, and system losses. The mode changes what you provide (e. Quickly set common performance ratios or panel wattages. Step 2: Select Panel Type Panel Type: Use the dropdown to select the type of solar panels you have.