Panel Output Calculator
See how much energy your solar panels produce per day, month, and year.
Free panel tool
Solar Panel Output Calculator
See how many kWh your solar panels produce per day, month, and year — with real-world losses applied.
Panel specs
Your location
Estimates based on average conditions. Actual output varies with weather, shading, panel angle, and temperature.
Frequently Asked Questions
How much electricity does a 400 watt solar panel produce per day?
A 400W solar panel produces approximately 1,600 to 2,400 Wh (1.6 to 2.4 kWh) per day depending on your location. In a region with 5 peak sun hours, a 400W panel produces about 400 × 5 × 0.82 (system derating) = 1,640 Wh per day. In a sunnier region with 6 hours, it produces about 1,968 Wh. Enter your panel wattage and sun hours above for your exact daily output.
How many kWh does a solar panel generate per month?
Multiply the daily output by 30. A 400W panel in a 5-sun-hour region produces about 1,640 Wh/day × 30 = 49.2 kWh per month. A 585W panel in the same location produces about 2,399 Wh/day × 30 = 72 kWh per month. Seasonal variation means summer months produce 20-30% more than winter months at the same location.
What is the actual output of a 585 watt solar panel?
A 585W panel rarely produces exactly 585W in real-world conditions. The 585W rating is measured under Standard Test Conditions (STC: 25°C, 1000 W/m² irradiance). In practice, real output is about 80-85% of rated wattage due to temperature derating, dust, wiring losses, and non-ideal sun angles. A 585W panel realistically produces 470-500W peak on a good day, and 2,000-2,900 Wh (2.0-2.9 kWh) of energy per day depending on sun hours.
How many kWh does a solar panel produce in winter?
Winter production is typically 40-60% of summer production depending on latitude. A 400W panel producing 2,000 Wh/day in summer may produce only 800-1,200 Wh/day in winter due to fewer sun hours, lower sun angle, and more cloud cover. In northern latitudes (UK, northern US, Canada), winter production can drop to 30-40% of summer levels. Size your system for winter production if you need consistent year-round output.
Do solar panels produce less on cloudy days?
Yes, but they still produce. On an overcast day, solar panels produce 10-25% of their rated output. On a partly cloudy day, they produce 50-70%. A 400W panel produces 40-100W on an overcast day and 200-280W on a partly cloudy day. This is why peak sun hours (which average in cloud cover) are used for sizing instead of assuming full sun all day. The calculator above uses peak sun hours to give you the realistic annual average.