How many solar panels do I need?

Divide your system size (kW) by panel wattage. For 6kW with 400W panels: 6000 ÷ 400 = 15 panels. Size system based on annual energy consumption.

How much electricity will my solar panels produce?

Daily kWh = System kW × Peak Sun Hours × 0.8 (efficiency). A 6kW system with 5 sun hours: 6 × 5 × 0.8 = 24 kWh/day or ~720 kWh/month.

What are peak sun hours?

Peak sun hours (PSH) represent the equivalent hours of 1000W/m² solar irradiance. It's not total daylight hours. US averages: 3-4 (NE), 4-5 (Midwest), 5-6 (Southwest).

What size solar system do I need?

Divide annual kWh by (365 × peak sun hours × 0.8). For 10,000 kWh/year with 4.5 PSH: 10000 ÷ (365 × 4.5 × 0.8) = 7.6 kW system.

How much money will solar save?

Multiply annual kWh production by electricity rate. A system producing 8,000 kWh at $0.15/kWh saves $1,200/year. Factor in net metering policies.

What affects solar panel efficiency?

Temperature (decreases above 25°C), shading, panel angle, dust/dirt, inverter losses, and wiring losses. Real-world efficiency is typically 75-85% of rated output.

Solar Panel Calculator

Our solar panel calculator helps homeowners and installers plan photovoltaic systems. Estimate how many panels you need based on energy consumption, calculate expected output based on location and panel specifications, and see potential cost savings over time.

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calendar_today Updated: April 2025

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Calculate

Output

Size

Panels

System Size

Peak Sun Hours

hrs

Panel Watts

Efficiency

Elec. Rate

$ /kWh

Results

kWh/day

Monthly Output

540 kWh

Yearly Output

6570 kWh

Panels Needed

13 panels

Roof Area

22.1 m²

Yearly Savings

$985.50

CO₂ Avoided

2628 kg/year

Input Values

Calculate

Energy Output

System Size Needed

Number of Panels

System Size

Panel Wattage

Peak Sun Hours

hrs/day

auto_awesome AI Analysis

Enter your values and calculate to receive AI-powered insights about your results.

wb_sunny Peak Sun Hours (US)

Southwest 5.5-6.5 hrs

Southeast 4.5-5.5 hrs

Midwest 4.0-5.0 hrs

Northeast 3.5-4.5 hrs

solar_power System Losses

🔌 Inverter: 3-5% loss
🌡️ Temperature: 5-15% loss
📊 Total efficiency: ~80%

How to Use This Calculator

Select Mode

Choose to calculate output, required system size, or panel count

Enter System Specs

Input system size or energy usage, panel wattage

Set Location Factor

Enter peak sun hours for your area

View Results

See energy production, savings, and panel requirements

The Formula

Solar output depends on panel wattage, sunlight hours in your location, and system efficiency losses (inverter, wiring, temperature, shading).

Daily Output (kWh) = Panel Watts × Peak Sun Hours × Efficiency

lightbulb Variables Explained

kWh Kilowatt-hours of energy produced
W Panel wattage (nameplate rating)
PSH Peak Sun Hours (varies by location)
η System efficiency (typically 75-85%)

tips_and_updates Pro Tips

Peak sun hours vary by location: 3-4 in cloudy areas, 5-6 in sunny regions

Account for 15-25% system losses (inverter, wiring, temperature)

South-facing panels (in Northern Hemisphere) produce most energy

Optimal tilt angle roughly equals your latitude

Panel output decreases ~0.5% per degree above 25°C

Shading from trees or buildings significantly reduces output

Most residential panels are 350-450W each

Proper solar system sizing depends on your energy consumption, available roof space, local sunlight, and budget. Most homes need 5-10kW systems to offset electricity bills.

Optimize output by choosing south-facing orientation, proper tilt angle (roughly equal to latitude), minimizing shading, and keeping panels clean.

Frequently Asked Questions

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