Solar Panel Calculator
Estimate solar energy production or determine how many panels you need.
Energy Output
Panels Needed
Presets (fills fields for quick start)
Estimated Daily Energy
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Enter values above
Monthly (30d)
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Yearly
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Formula
E = W × N × h × η
Solar Energy Formulas
Edaily = Ppanel × N × h × η
N = Eload / (Ppanel × h × η)
Ppanel – panel wattage (W)
N – number of panels
h – peak sun hours per day (h)
η – system efficiency (0‑1, e.g., 0.8)
Energy is in watt‑hours (divide by 1000 for kWh)
N – number of panels
h – peak sun hours per day (h)
η – system efficiency (0‑1, e.g., 0.8)
Energy is in watt‑hours (divide by 1000 for kWh)
People Also Ask
☀️ What are peak sun hours?
📊 How do I estimate my daily load?
🔧 What factors affect system efficiency?
🏠 How many solar panels do I need for an average home?
📈 How much energy can a 400W panel produce per day?
🌍 Typical sun hours by region?
Understanding Solar Panel Calculations
The energy produced by a solar panel depends on its wattage, the number of panels, the amount of sunlight (peak sun hours), and system losses (efficiency).
Peak Sun Hours
One peak sun hour equals 1 kWh/m² of solar energy. It is not the same as daylight hours. For example, a location might get 5 peak sun hours even though the sun is up for 12 hours.
Average Peak Sun Hours (US Examples)
| Region | Peak Sun Hours/day |
|---|---|
| Arizona (sunny) | 6.5 |
| California (coastal) | 5.0 |
| Texas | 5.2 |
| New York | 4.0 |
| Pacific Northwest | 3.5 |
Detailed FAQs
What is system efficiency and why is it important?
System efficiency accounts for losses from the inverter, wiring, dust, temperature, and shading. Typical values are 75–85%. If ignored, your estimate will be too optimistic.
Can I use this for off‑grid or grid‑tied systems?
Yes, the energy calculation works for both. For off‑grid you also need battery storage, which is not covered here.