How Many Panels Do I Need for Solar? – Step-by-Step Calculation 2026
19/04/2026
"How many panels do I need?" — this is the question every homeowner asks before buying. Here you will find the answer in numbers, not guesswork.
Step 1: Find your annual consumption
Look at your electricity bill for the last 12 months — not just the most recent one. In winter, you consume 3× more energy than in summer!
| Type of Residence | Annual Consumption |
|---|---|
| Small apartment (1-2 people) | 2,000–3,000 kWh |
| Medium-sized home (3-4 people) | 4,000–6,000 kWh |
| Large home (5+ people) | 6,000–10,000 kWh |
| Small business | 8,000–20,000 kWh |
Step 2: Sunshine in your area
| Region | kWh/kWp per year |
|---|---|
| Crete, Islands | 1,600–1,700 |
| Athens, Peloponnese | 1,450–1,550 |
| Thessaloniki, Central Greece | 1,300–1,450 |
| Northern Greece | 1,150–1,300 |
Step 3: The calculation method
Number of panels = Annual consumption (kWh) ÷ (kWh/kWp × Panel power in kW)
Real-life example
Kostas in Patras consumes 5,400 kWh/year. Region: Peloponnese (1,500 kWh/kWp). Panels: Longi 450W.
5,400 ÷ (1,500 × 0.45) = 8 panels = 3.6 kWp system
Cost: ~€5,800 | Payback period: 4 years
💡 Tip: Add 10-15% more to the number for losses due to shade, dust, and temperature. Better to have too much than too little.
How much roof space do I need?
| Number of Panels (450W) | Roof Space | Power |
|---|---|---|
| 6 panels | ~14 m² | 2.7 kWp |
| 8 panels | ~18 m² | 3.6 kWp |
| 10 panels | ~23 m² | 4.5 kWp |
| 12 panels | ~28 m² | 5.4 kWp |
FAQ
Can I add more panels later?
Yes! The system can be easily expanded with additional panels and batteries.
What if I don't have enough roof space?
You can install panels on the ground or in an external setup. A study will determine the best solution.
Is it worth installing a larger system than I need?
Yes, if you're thinking of buying an EV or a heat pump in the future. It's better to plan with room for growth.