How Many Solar Panels Do I Need? — Calculator & Guide
The Simple Formula
The number of solar panels you need depends on three factors: your electricity consumption, the panel wattage, and your location's solar irradiance. The basic formula is:
Number of panels = Daily energy need (kWh) ÷ (Panel wattage × Peak sun hours × System efficiency)
Step 1: Determine Your Energy Consumption
Check your electricity bill for monthly consumption in kWh. Divide by 30 to get your daily average.
| Home Type (UAE) | Monthly Usage | Daily Average |
|---|---|---|
| Small apartment | 500–1,000 kWh | 17–33 kWh |
| Medium villa | 2,000–3,000 kWh | 67–100 kWh |
| Large villa | 4,000–6,000 kWh | 133–200 kWh |
| Commercial building | 10,000–50,000 kWh | 333–1,667 kWh |
Step 2: Know Your Peak Sun Hours
Peak sun hours (PSH) represent equivalent hours of full 1,000 W/m² sunlight per day.
- Dubai / Abu Dhabi: 5.5–6.0 PSH
- Riyadh: 5.8–6.3 PSH
- Cairo: 5.2–5.7 PSH
- Amman: 5.0–5.5 PSH
- London: 2.5–3.0 PSH
- Berlin: 2.8–3.3 PSH
Step 3: Account for System Losses
Real-world systems lose 15–25% of rated capacity due to temperature, wiring, inverter efficiency, soiling, and shading. A typical system efficiency factor is 0.80 (80%).
Step 4: Calculate Panel Count
Example: Medium Villa in Dubai
Monthly usage: 2,500 kWh → Daily: 83 kWh
Using LONGi Hi-MO 7 (590W) in Dubai (5.5 PSH):
Daily output per panel = 590W × 5.5h × 0.80 = 2.60 kWh
Panels needed = 83 ÷ 2.60 = 32 panels
System size = 32 × 590W = 18.9 kW
Quick Reference Table
| Daily Usage | LONGi Hi-MO 7 (590W) | LONGi Hi-MO 6 (540W) | LONGi Hi-MO 6 (430W) |
|---|---|---|---|
| 30 kWh | 12 panels (7.1 kW) | 13 panels (7.0 kW) | 16 panels (6.9 kW) |
| 50 kWh | 20 panels (11.8 kW) | 21 panels (11.3 kW) | 27 panels (11.6 kW) |
| 80 kWh | 31 panels (18.3 kW) | 34 panels (18.4 kW) | 43 panels (18.5 kW) |
| 120 kWh | 47 panels (27.7 kW) | 51 panels (27.5 kW) | 64 panels (27.5 kW) |
Roof Space Requirements
Each panel requires approximately:
- LONGi Hi-MO 7 (590W): 2.58 m² per panel
- LONGi Hi-MO 6 (540W): 2.38 m² per panel
- LONGi Hi-MO 6 (430W): 1.95 m² per panel
Add 15–20% for spacing between rows, walkways, and setbacks from roof edges.
Factors That Affect Your Calculation
- Net metering: If your utility offers net metering (like DEWA's Shams Dubai), you can size for 100% offset
- Battery storage: If adding batteries, you may want to oversize by 20–30%
- Future expansion: Plan for electric vehicle charging or additional loads
- Shading: Reduce expected output by 5–15% if partial shading exists
Frequently Asked Questions
How many solar panels do I need for a 3-bedroom house?
In the UAE, a 3-bedroom house typically uses 2,000–3,000 kWh/month. You would need 25–40 LONGi Hi-MO 7 panels (15–24 kW system) to offset most or all of your electricity consumption.
Can solar panels power my entire house?
Yes, if you have sufficient roof space. A properly sized system with net metering can offset 100% of your electricity bill. In the UAE, this typically requires 15–30 kW for a villa.
How many panels for a 10 kW system?
With LONGi Hi-MO 7 (590W): 17 panels. With Hi-MO 6 (540W): 19 panels. With Hi-MO 6 (430W): 24 panels.
Frequently Asked Questions
How many solar panels for a 3-bedroom house?
In the UAE, 25–40 LONGi Hi-MO 7 panels (15–24 kW) to offset 2,000–3,000 kWh/month consumption.
Can solar panels power my entire house?
Yes, with sufficient roof space and net metering. In the UAE this typically requires 15–30 kW for a villa.
How many panels for a 10 kW system?
With LONGi Hi-MO 7 (590W): 17 panels. With Hi-MO 6 (540W): 19 panels. With Hi-MO 6 (430W): 24 panels.
