Calculate how much energy your solar panels will produce. Estimate solar power generation based on system size, efficiency, and location.
Calculate solar panel energy production based on system size and location.
The Solar Panel Energy Calculator helps homeowners and installers accurately estimate electricity production from photovoltaic (PV) systems. Understanding how much energy solar panels generate is essential for sizing your system correctly, calculating potential savings, and making informed decisions about your renewable energy investment.
Solar energy production depends on several interconnected factors: your geographic location determines available sunlight, panel specifications define conversion efficiency, and installation conditions affect real-world performance. A 6kW system in Phoenix, Arizona produces significantly more electricity than the same system in Seattle, Washington—understanding these variables prevents costly over- or under-sizing mistakes.
According to the U.S. Department of Energy, residential solar installations have grown over 30% annually, with the average American home now able to offset 80-100% of electricity consumption with a properly sized system. This calculator uses industry-standard formulas and regional solar irradiance data to provide accurate production estimates for your specific situation.
Panel Wattage = Rated power of each panel in watts (e.g., 400W)
Peak Sun Hours = Hours of 1,000 W/m² solar irradiance per day (varies by location)
Efficiency Factor = System losses from inverter, wiring, temperature (typically 0.75-0.85)
For total system output, multiply by number of panels. Monthly production = Daily output × 30 days.
Different solar technologies offer varying efficiency levels, costs, and performance characteristics:
| Panel Type | Efficiency | Cost/Watt | Lifespan | Best For |
|---|---|---|---|---|
| Monocrystalline | 18-22% | $0.30-$0.50 | 25-30 years | Limited roof space, maximum output |
| Polycrystalline | 15-17% | $0.25-$0.40 | 25-30 years | Budget installations, larger roofs |
| Thin-Film | 10-13% | $0.20-$0.35 | 15-20 years | Flexible applications, low-light areas |
Monocrystalline panels dominate residential installations due to superior efficiency and space optimization.
Peak sun hours measure equivalent hours of maximum solar intensity (1,000 W/m²) per day—the critical factor in calculating solar production:
| Region | Peak Sun Hours | Annual kWh per kW | Example Cities |
|---|---|---|---|
| Southwest US | 6.0-7.0 | 1,800-2,100 | Phoenix, Las Vegas, Albuquerque |
| California | 5.5-6.5 | 1,600-1,900 | Los Angeles, Sacramento, San Diego |
| South/Southeast | 5.0-5.5 | 1,500-1,700 | Miami, Houston, Atlanta |
| Midwest | 4.0-4.5 | 1,200-1,400 | Chicago, Denver, Kansas City |
| Northeast | 3.5-4.5 | 1,100-1,350 | Boston, New York, Philadelphia |
| Pacific Northwest | 3.5-4.0 | 1,000-1,200 | Seattle, Portland, Vancouver |
Data based on NREL's National Solar Radiation Database. Actual values vary by microclimate and elevation.
❌ Overestimating peak sun hours: Daylight hours ≠ peak sun hours. A location with 12 hours of daylight may only have 4-5 peak sun hours of usable solar intensity. Use NREL data, not assumptions.
❌ Ignoring shading impacts: Nearby trees, chimneys, or buildings casting shadows—even partial shade on one panel—can reduce entire string output by 25-80%. Conduct a shade analysis before installation.
❌ Using nameplate ratings without derating: A 400W panel doesn't produce 400W in real conditions. Temperature, wiring, and inverter losses reduce actual output to 75-85% of rated capacity.
❌ Forgetting seasonal variation: Summer production can be 2x winter output. Size systems for annual average, not peak summer performance.
❌ Not accounting for panel degradation: Solar panels lose 0.5-0.8% efficiency annually. Factor this into 25-year production estimates.
Match your system size to your electricity consumption and offset goals:
| Monthly Usage | Recommended System | Number of Panels* | Roof Space Needed | Annual Production** |
|---|---|---|---|---|
| 500 kWh | 4 kW | 10 panels | 200 sq ft | 5,800 kWh |
| 750 kWh | 5.5 kW | 14 panels | 280 sq ft | 8,000 kWh |
| 1,000 kWh | 7 kW | 18 panels | 360 sq ft | 10,200 kWh |
| 1,250 kWh | 9 kW | 23 panels | 460 sq ft | 13,100 kWh |
| 1,500 kWh | 11 kW | 28 panels | 560 sq ft | 16,000 kWh |
*Based on 400W panels. **Based on 4.5 peak sun hours average; adjust for your region.
Sources & Methodology: Solar production calculations based on industry-standard PV performance formulas. Regional peak sun hours data from the National Renewable Energy Laboratory (NREL) National Solar Radiation Database. Panel efficiency specifications per manufacturer averages and NREL module performance standards. System loss factors (derating) follow NREL PVWatts methodology. For location-specific estimates, consult the NREL PVWatts Calculator and U.S. Department of Energy Solar Energy Technologies Office. Calculator updated January 2026.
A typical 400-watt residential solar panel produces 1.2-2.4 kWh per day depending on your location's peak sun hours. In sunny Arizona (6+ peak sun hours), a single panel generates about 2.4 kWh daily, while in the Pacific Northwest (3.5-4 hours), expect closer to 1.2-1.6 kWh. A complete 6kW home system (15 panels) produces 18-36 kWh daily, enough to power most households. Actual output varies by season, panel orientation, shading, and system efficiency (typically 75-85% after inverter and wiring losses).
Use this formula: Daily Output (kWh) = Panel Wattage × Number of Panels × Peak Sun Hours × Efficiency Factor (0.75-0.85). For example, with 15 panels at 400W each in an area with 5 peak sun hours: 400W × 15 × 5 hours × 0.80 = 24 kWh/day or 720 kWh/month. To size your system, divide your monthly electricity usage by 30 days, then divide by (peak sun hours × 0.80 efficiency) to get the kW system size needed. Most homes use 900-1,200 kWh monthly, requiring a 6-10 kW system.
Seven key factors impact solar panel performance: 1) Panel orientation—south-facing at an angle equal to your latitude is optimal. 2) Shading—even partial shade on one panel can reduce entire string output by 25-80%. 3) Temperature—panels lose 0.3-0.5% efficiency per degree above 25°C (77°F). 4) Soiling—dust, pollen, and bird droppings can reduce output 2-5%. 5) Panel age—expect 0.5-0.8% degradation annually. 6) Inverter efficiency—quality inverters convert 95-98% of DC to AC power. 7) Wiring losses—typically 1-3% depending on installation quality.