You want to find out how many photovoltaic panels do you need? for your home or business? Use the interactive EcoSolaris calculator — it tells you in 30 seconds the optimal system size, estimated annual production, approximate cost and savings over 25 years.
⚡ Photovoltaic System Sizing Calculator
Search on the last electricity bill (or collect 12 months).
Residential house
Apartment
Company / headquarters
Farm / shed
On-grid (prosumer) — the most cost-effective
Hybrid (with backup batteries)
Off-grid (100% autonomous)
function ecoPvCalc() {
var consumption = parseFloat(document.getElementById(“pv-consumption”).value);
var type = document.getElementById(“pv-type”).value;
var system = document.getElementById(“pv-system”).value;
var out = document.getElementById("pv-result");
if (!consumption || consumption < 50) { out.innerHTML = "
"; return; }
annual lime = consumption * 12;
lime oresore = 4.3; // Romanian average
var kwp = Math.ceil(annual / (oresore * 365) * 1.1 * 10) / 10;
var panels = Math.ceil(kwp * 1000 / 450);
var surface = Math.ceil(panels * 2.2);
var pret_min = system===”hybrid”? kwp*7000 : (system===”offgrid”? kwp*9000 : kwp*4500);
var pret_max = system===”hybrid”? kwp*9500 : (system===”offgrid”? kwp*12000 : kwp*6000);
var producti_an = Math.round(kwp * oresoare * 365);
var savings_year = Math.round(products_year * 0.85);
var roi_ani = Math.ceil((min_price + max_price)/2 / savings_year);
var green_house = system===”ongrid” && type===”house” && kwp <= 6 ? 20000 : 0;
out.innerHTML = "
“
📊 Sizing result
” +
“
| System required: | ” + kwp.toFixed(1) + ” kwp |
| Number of panels (450W): | ” + panels + ” pieces |
| Roof area: | ~" + area + " m² |
| Estimated annual production: | ” + producti_an.toLocaleString(“ro”) + ” kWh |
| Annual savings (~0.85 RON/kWh): | ” + economii_an.toLocaleString(“ro”) + ” RON |
| Turnkey system cost: | ” + Math.round(pret_min).toLocaleString(“ro”) + ” – ” + Math.round(pret_max).toLocaleString(“ro”) + ” RON |
| Green House Voucher 2026: | – 20,000 RON |
| Estimated ROI: | ~” + roi_ani + ” years |
” +
“
"💡 These estimates are indicative. For a personalized offer, ask for a free consultation or call +40 728 022 022.” +
“
“;
}
How to correctly calculate the size of the photovoltaic system
For optimal sizing, you need to consider 4 key factors:
- Annual consumption of electricity (kWh) — the sum of 12 months of bills
- Equivalent sunshine hours in your area — Romania: 3.8-4.7 h/day on average
- System losses — inverter, cables, temperature (5-10%)
- Safety margin — we recommend +10-15% for cloudy years or increasing consumption
The practical formula
Example: 5000 kWh ÷ (4.3 × 365) × 1.1 = 3.5 kWp [#$$#]
Quick table: consumption vs system required
| Monthly consumption (kWh) | System required | Panels (450W) | On-grid cost |
|---|---|---|---|
| 100-200 | 3 kWp | ~7 | 14,000-18,000 RON |
| 200-350 | 5 kWp | ~12 | 22,000-30,000 RON |
| 350-500 | 8 kWp | ~18 | 36,000-48,000 RON |
| 500-800 | 10 kWp | ~23 | 42,000-58,000 RON |
| 800+ | 15-30 kWp | 35-70 | 60,000-150,000 RON |
