How many solar panels does my house need? The simple method

3, 8 or 16 panels? The answer is in your electricity bill and the way your roof faces.

"How many panels do I need?" — it is always the first question. Here is the method we use to size a system, explained plainly.

Step 1: start from your consumption

Look at your annual electricity bill (in kWh, not in euros). A French household typically uses:

• 2,500 to 4,000 kWh a year: small household, heating not electric
• 6,000 to 9,000 kWh a year: family, electric hot water cylinder
• 10,000 to 15,000 kWh a year: all-electric, heat pump, electric car

Step 2: convert to peak output

In northern France, 1 kWp facing the right way produces roughly 950 to 1,100 kWh a year. In the south, up to 1,400. The simple rule for self-consumption: aim for an output that covers what you use during the day, without oversizing.

• Bill around 2,500 kWh a year → 2 to 3 kWp (4 to 6 panels of 520 Wp)
• Bill around 6,000 kWh a year → 4 to 6 kWp (8 to 12 panels)
• Bill of 10,000 kWh a year or more → 6 to 9 kWp (12 to 18 panels), and a battery is strongly advised

Step 3: orientation and pitch

• Due south, 30-35°: ideal, 100% of the potential
• South-east or south-west: very good, around 95%
• East plus west: around 85%, but production is spread more evenly across the day — sometimes the better option for self-consumption
• North: avoid

Step 4: oversize... or not

A sales rep will usually try to sell you as many panels as possible. Yet without a battery, exported surplus earns only a few cents per kWh: producing far more than you use pays very little. Two rational strategies: size it tightly, or pair it with a battery and a solar diverter so every kWh produced is put to work.

Run the numbers for your own house

Our free calculator does this in 30 seconds from your monthly bill and your roof orientation. And for precise sizing (shading, separate roof faces, future plans such as a heat pump or an electric car), request a free assessment — no obligation.