Step 1 — Calculate Your Daily Energy Consumption
Before you can size any solar system, you must know how much electricity you use each day in kilowatt-hours (kWh). The formula for each appliance is:
Example: 2 ceiling fans (75W each) running 12 hours/day = (75 × 2 × 12) ÷ 1000 = 1.8 kWh/day. Sum this across all your appliances for your total daily load.
Step 2 — Determine Your Solar System Size (kW)
Solar panels don't produce their rated power all day. You need to account for peak sun hours — the number of hours per day your panels receive full (1,000 W/m²) sunlight — and system efficiency losses from heat, wiring, and inverters.
The 0.8 factor represents 80% overall system efficiency — accounting for wiring losses (~2%), heat derating (~5%), inverter conversion losses (~5%), and soiling (~3%). This is the globally accepted estimate used by NREL and most solar installers.
Peak Sun Hours by Region
Step 3 — Calculate Number of 550W Solar Panels
We always round up (ceiling function) because you cannot install half a panel. Modern residential and commercial installations use 550W monocrystalline PERC panels — the 2024–2026 industry standard offering the best power-to-size ratio.
Real-World Examples
| Scenario | Daily kWh | System kW | 550W Panels |
|---|---|---|---|
| Small Home (2 fans, 6 lights, fridge) | 3.5 kWh | 0.875 kW | 2 panels |
| Medium Home + 1 Inverter AC | 14 kWh | 3.5 kW | 7 panels |
| Large Home + 2 ACs | 30 kWh | 7.5 kW | 14 panels |
Get Your Exact Panel Count Instantly
Skip the manual math. Enter your appliances into our free solar calculator and get your precise system size, panel count, inverter, and battery specs in seconds.
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