How Many kW Does a House Need for Photovoltaics? Complete Guide 2026
19/04/2026
"How many kW should I install?" — this is the question that determines whether you save or waste money. Here you will find the exact answer.
Step 1: Consumption per house size
| House Size | People | Monthly/kWh | Annual |
|---|---|---|---|
| Apartment 50sqm | 1–2 | 150–250 kWh | 1,800–3,000 kWh |
| Medium house 120sqm | 3–4 | 300–500 kWh | 3,600–6,000 kWh |
| Large house 200sqm | 5+ | 500–1,000 kWh | 6,000–12,000 kWh |
Step 2: Calculation type
System kW = Annual consumption (kWh) ÷ 1,400
| Annual Consumption | Recommended System | Cost |
|---|---|---|
| 2,400 kWh | 3 kW | ~4,500€ |
| 5,000 kWh | 5 kW | ~7,000€ |
| 8,000 kWh | 8 kW | ~11,000€ |
| 12,000 kWh | 10 kW | ~14,000€ |
Real-life example
Alexandros in Athens consumed 5,600 kWh/year. Calculation: 5,600 ÷ 1,400 = 4 kW. He chose a 5kW system with Longi panels and a Victron MPPT. Cost: 7,200€. Annual savings: 1,500€. Payback period: 4.8 years.
💡 Tip: If you're considering buying an EV or a heat pump in the next 2-3 years, design the system with room for growth from the start.
FAQ
Is it worth installing a larger system than I need?
Yes, if you are considering future needs (EV, heat pump). With Net Billing, you sell the surplus to the grid.
Do I need a battery?
It is not essential for an on-grid system. If you want autonomy or backup during outages, add a Pytes LiFePO4.
How much roof space do I need?
Approximately 2-2.5 m² per 450W panel. For 5kW, you need about 22-25 m² of roof space.