How many solar panels do I need for my house?
Resposta rápida
The sizing rule
The number of panels comes from your consumption, not the size of your house. Take your annual consumption (the sum of the kWh on a year of bills) and divide by one panel's output:
Number of panels ≈ annual consumption (kWh) ÷ ~700 kWh/panel/year
Example: a home using 4,200 kWh/year → 4,200 ÷ 700 ≈ 6 panels to cover annual consumption (in practice this is adjusted to daytime usage and roof space).
Table by household type and consumption
| Type | Typical annual use | Panels (approx.) | Power |
|---|---|---|---|
| 2-bed (T2) | 2,500 – 3,500 kWh | 5 to 8 | 3 to 4 kWp |
| 3-bed (T3) | 3,500 – 5,000 kWh | 8 to 11 | 4 to 5 kWp |
| 4-bed (T4) | 5,000 – 7,000 kWh | 10 to 13 | 5 to 6 kWp |
What else matters
- How much you use during the day — more daytime use means less surplus (or less need for a battery).
- Your region — from the northern coast (~1,420 kWh/kWp) to the Algarve (~1,750 kWh/kWp), the same power produces more in the south.
- Roof orientation and tilt.
- Shading from chimneys, trees or neighbouring buildings.
More isn't better
Want the exact number for your home? The simulator works out the power and number of panels from your bill.
Frequently asked questions
How many solar panels do I need for a house?
A typical home in Portugal needs 6 to 12 panels (around 3 to 6 kWp), depending on consumption. A 2-bed home is around 5–8 panels, a 3-bed 8–11 and a 4-bed 10–13. The exact number depends on your real usage and available roof area.
How is the number of panels calculated?
Divide your annual consumption (kWh, on your bill) by the annual output of each panel. In Portugal, a ~450 W panel produces roughly 650 to 790 kWh per year. For example, a home using 4,000 kWh/year needs about 6 to 8 panels.
How much space does each panel take?
A modern panel takes about 1.8 to 2 m². A 5 kWp system (10–11 panels) takes roughly 20 m² of well-oriented roof.
Are more panels always better?
No. An oversized system exports a lot of cheap surplus to the grid, slowing your payback. The ideal is to size to your real consumption — that's what maximises savings.