Tutorials
How to size a solar power plant
From your electricity bill to the number of panels — step by step, without complex formulas.
1 min read
For a first estimate you only need your electricity bill and a few simple numbers.
Step 1: daily consumption
Take the monthly consumption (kWh) from your bill and divide by 30. For example, 600 kWh per month is 20 kWh per day.
Step 2: peak sun hours
In much of western Iran, average peak sun hours are around 5 to 5.5. Allow about 20% for system losses (heat, dust, cables and the inverter).
Step 3: capacity and panel count
20 ÷ (5.5 × 0.8) ≈ 4.5 kW. With 550 W panels, that is about 9 panels.
- Inverter rating: equal to or a little below the panel capacity
- Area needed: about 2.5–3 m² per panel
- Off-grid systems: size the batteries separately
Our engineering calculator does this in seconds. A final design also checks roof tilt, shading and orientation.
Need advice for your own project?
Use our calculator for a quick estimate, or talk to an engineer for free.