Solar Panel Calculator

Estimate how many solar panels you need for your daily energy use.

Daily energy use (kWh)

Peak sun hours

Panel rating (W)

System efficiency (%)

Panels needed (panels) 19

System size (kW) 7.6

Formula: panels = daily kWh ÷ (sun hours × panel kW × efficiency)

Step-by-step with your numbers:

1. Values used:

2. Daily energy use = 30 kWh

3. Peak sun hours = 5

4. Panel rating = 400 W

5. System efficiency = 80 %

7. Panels needed = 19panels

8. System size = 7.6kW

Did we solve your problem today?

Roughly size a rooftop solar array from your energy use and local sunshine.

The math behind it

Each panel makes ≈ sun hours × panel kW × system efficiency per day. Panels = daily use ÷ that, rounded up.

30 kWh/day, 5 sun hours, 400 W panels, 80% efficiency → 1.6 kWh/panel → 19 panels (7.6 kW).

What are peak sun hours?

The equivalent hours per day of full 1,000 W/m² sunlight — varies by location and season.