Solar Panel Output Calculator - Estimate Energy Production

Calculate exactly how much electricity your solar panel system will generate. Enter your panel specifications, local sun hours, and system efficiency to get precise daily, monthly, and yearly energy output estimates.

☀️ Panel Configuration

Panel Wattage (W)

Number of Panels

Sun Hours per Day

Efficiency (%)

📊 Energy Production Estimates

Daily Output

Monthly Output

Yearly Output

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Professional installation, optimal panel orientation, and regular maintenance can boost your solar energy production by 15-25%. Get expert advice today.

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How Much Energy Do Solar Panels Actually Produce?

Solar panel output depends on three primary factors: the panel's rated wattage, the number of peak sun hours in your location, and real-world losses from shading, temperature, and inverter inefficiency. A standard 400-watt residential solar panel in a location with 5 peak sun hours produces roughly 2 kWh per day, or about 60 kWh per month.

But rated wattage isn't the full story. The NREL PVWatts Calculator applies a performance ratio of about 80-86% to account for real-world conditions — meaning a 400W panel actually produces closer to 320-340 watts under typical operating conditions.

Factors That Reduce Solar Panel Output

Temperature: Solar panels lose 0.3-0.5% efficiency for every degree Celsius above 25°C (77°F). In extreme summer heat, output drops 10-15%.
Shading: Even partial shading of one panel can reduce an entire string's output by 20-40%. Microinverters or power optimizers mitigate this.
Panel orientation: South-facing panels produce 10-25% more than east- or west-facing panels in the Northern Hemisphere.
Roof tilt: The optimal angle equals your latitude. Panels mounted significantly above or below this angle produce 5-15% less.
Dirt and debris: Dirty panels lose 2-6% output. Annual cleaning is recommended in dusty areas.
Inverter efficiency: String inverters are 95-97% efficient. Microinverters are 96-98% efficient. This small difference compounds over 25 years.

Frequently Asked Questions About Solar Panel Output

How many kWh does a single solar panel produce per day?▼

A standard 400W panel produces 1.6-2.4 kWh per day depending on your location's sun exposure. In Arizona or California (6+ peak sun hours), expect 2.0-2.4 kWh/day. In the Pacific Northwest (3-4 peak sun hours), expect 1.2-1.6 kWh/day. Multiply by the number of panels in your system for total daily production.

Do solar panels produce less in winter?▼

Yes, typically 30-50% less than summer production due to shorter days and lower sun angles. However, cold temperatures actually improve panel efficiency — panels produce more power per hour of sunlight in cold weather than in heat. Snow coverage can block production entirely, but panels are slick and snow usually slides off quickly.

How much output do solar panels lose over time?▼

Quality solar panels degrade at approximately 0.5% per year. After 25 years, they still produce 87-90% of their original output. Most manufacturers guarantee at least 80% output at year 25. This degradation is factored into production estimates and ROI calculations.

Should I use the PVWatts calculator to verify estimates?▼

Yes, NREL's PVWatts is the gold standard for solar production estimates. It uses satellite-derived solar resource data and accounts for your exact location, panel tilt, azimuth, and system losses. Always compare your installer's production estimate against PVWatts to ensure it's realistic.