Solar Panel Output Calculator
Calculate how much electricity your solar panels will produce per day, month, and year.
Enter panel wattage, sun hours, and efficiency.
Solar panel output depends on panel wattage, sunlight hours, system efficiency, and your local climate. Calculating expected energy production and financial savings helps you evaluate whether solar is right for your home.
Key formulas: Daily Energy Output (kWh) = Panel Wattage (kW) × Peak Sun Hours × System Efficiency Annual Output = Daily Output × 365 Annual Savings = Annual Output × Electricity Rate ($/kWh) Payback Period (years) = System Cost ÷ Annual Savings
What each variable means:
- Panel Wattage: rated output under Standard Test Conditions (STC): 1,000 W/m² irradiance, 25°C cell temperature. Common residential panels: 300W–450W each.
- Peak Sun Hours (PSH): the equivalent hours of full-intensity sunshine per day at your location. Not the same as daylight hours. Varies from ~2.5 PSH (Seattle) to ~6.5 PSH (Phoenix).
- System Efficiency: accounts for inverter losses (~4%), temperature derating (~5–10%), shading, soiling, wiring losses. Typically 75–85% total.
- Electricity Rate: what your utility charges per kWh. U.S. average ≈ $0.16/kWh (2024), but ranges from $0.09 (Louisiana) to $0.33+ (Hawaii, California).
U.S. peak sun hours by city:
- Phoenix, AZ: 6.5 PSH
- Dallas, TX: 5.5 PSH
- Atlanta, GA: 5.0 PSH
- Denver, CO: 5.5 PSH
- New York, NY: 4.5 PSH
- Seattle, WA: 2.5 PSH
Worked example: 10 panels × 400W = 4,000W = 4 kW system. Location: Atlanta (5.0 PSH). System efficiency: 80%. Daily output = 4 kW × 5.0 × 0.80 = 16 kWh/day Annual output = 16 × 365 = 5,840 kWh Annual savings = 5,840 × $0.13 = $759/year System cost (after 30% federal tax credit): $12,000. Payback = $12,000 ÷ $759 = 15.8 years
Federal solar tax credit (ITC): 30% of system cost deducted from federal income taxes (available through 2032 at 30%, then steps down). This significantly improves payback calculations.