☀️ Solar Panel Sizing Calculator
Find out how many watts of solar panels you need based on your actual daily energy consumption.
Typical cabin: 1000–3000 Wh · House: 5000–10000 Wh
US avg: 4–6 hrs · Southwest: 6–7 · Northeast: 3.5–4.5
Use 75–80% for MPPT controller · 65–70% for PWM
Your Results
How We Calculate Solar Panel Size
The formula is straightforward:
Example: 3,000 Wh ÷ (5 hours × 0.80) = 750W of panels
What is System Efficiency?
Solar panels don't perfectly convert their rated output into usable power. Losses come from: wiring resistance (~2–3%), MPPT controller efficiency (~5%), battery charging losses (~5–10%), and temperature derating. We use 80% as a realistic middle estimate for an MPPT-based system.
What are Peak Sun Hours?
Peak sun hours (PSH) is not the number of daylight hours. It's a measure of how much total solar energy hits your location — standardized to the equivalent of 1 hour at peak (1,000 W/m²) intensity. The US average is about 4.5 PSH, ranging from ~3.5 in Seattle to ~7 in Arizona.
Next Steps After Sizing Your Panels
Once you know your panel wattage, you'll need to:
- Size your battery bank (see our Battery Sizing Calculator)
- Choose an MPPT charge controller sized for your panels + battery voltage
- Choose an inverter sized for your largest simultaneous loads