One of the first questions when planning a solar PV system: how many solar panels will I need? The answer depends on two variables—your target system size in kilowatts peak (kWp) and the wattage of the panels you choose.

This guide provides a complete panel count reference table covering system sizes from 3 kWp to 20 kWp across all common panel wattages available in 2026. We also explain the formula, string configuration options, and roof area requirements for each combination.

                    Quick Reference: A 5 kWp system needs 10 panels at 550W (5.50 kWp actual) or 9 panels at 580W (5.22 kWp actual). A 10 kWp system needs 19 panels at 550W or 18 panels at 580W. See the full table below.
                

The Formula

Panel Count = (Target System Size in kWp × 1000) ÷ Panel Wattage (W)

Always round up to the next whole panel.

Example: 5 kWp system with 550W panels:

(5 × 1000) ÷ 550 = 9.09 → 10 panels (5.50 kWp actual)

Example: 10 kWp system with 550W panels:

(10 × 1000) ÷ 550 = 18.18 → 19 panels (10.45 kWp actual)

Why Round Up? Rounding up ensures you meet or exceed your target system size. The small oversize (typically 5-10%) is beneficial because solar panels rarely operate at STC nameplate power due to real-world conditions (heat, soiling, wiring losses).

Complete Panel Count Reference Table

The table below shows the exact number of panels needed for each system size and panel wattage combination. The actual kWp achieved is shown in parentheses.

Target kWp	400W Panels	450W Panels	550W Panels	580W Panels	650W Panels	700W Panels
3 kW	8 (3.20)	7 (3.15)	6 (3.30)	6 (3.48)	5 (3.25)	5 (3.50)
4 kW	10 (4.00)	9 (4.05)	8 (4.40)	7 (4.06)	7 (4.55)	6 (4.20)
5 kW	13 (5.20)	12 (5.40)	10 (5.50)	9 (5.22)	8 (5.20)	8 (5.60)
6 kW	15 (6.00)	14 (6.30)	11 (6.05)	11 (6.38)	10 (6.50)	9 (6.30)
7 kW	18 (7.20)	16 (7.20)	13 (7.15)	13 (7.54)	11 (7.15)	10 (7.00)
8 kW	20 (8.00)	18 (8.10)	15 (8.25)	14 (8.12)	13 (8.45)	12 (8.40)
9 kW	23 (9.20)	20 (9.00)	17 (9.35)	16 (9.28)	14 (9.10)	13 (9.10)
10 kW	25 (10.00)	23 (10.35)	19 (10.45)	18 (10.44)	16 (10.40)	15 (10.50)
12 kW	30 (12.00)	27 (12.15)	22 (12.10)	21 (12.18)	19 (12.35)	18 (12.60)
15 kW	38 (15.20)	34 (15.30)	28 (15.40)	26 (15.08)	24 (15.60)	22 (15.40)
20 kW	50 (20.00)	45 (20.25)	37 (20.35)	35 (20.30)	31 (20.15)	29 (20.30)

                    Reading the Table: For a 10 kW target with 550W panels, you need 19 panels, giving you an actual system size of 10.45 kWp (4.5% oversize). For a 10 kW target with 580W panels, you need 18 panels (10.44 kWp actual), which splits evenly across two MPPT inputs (9+9).
                

String Configuration by System Size

Once you know the panel count, you need to distribute them across your inverter's MPPT inputs. Most residential inverters have 1 or 2 MPPT trackers. Here are recommended string configurations for 550W panels:

System Size	Panels	Single MPPT	Dual MPPT (Even)	Dual MPPT (Odd)
3 kW	6	1S × 6	3 + 3	—
5 kW	10	1S × 10	5 + 5	—
6 kW	11	1S × 11	—	6 + 5
8 kW	15	1S × 15	—	8 + 7
10 kW	19	—	—	10 + 9
12 kW	22	—	11 + 11	—
15 kW	28	—	14 + 14	—
20 kW	37	—	—	19 + 18

Odd Panel Count Balancing: When you have an odd number of panels (e.g., 19 for 10 kWp), a dual-MPPT inverter handles the imbalance since each MPPT tracks independently. However, an even split (e.g., 18 panels with 580W modules) is generally preferred for cleaner wiring and easier troubleshooting.

Roof Area Required

The area needed depends on panel count, panel dimensions, and the mandatory 30% fire safety setback. For 550W panels (2.58 m² each) and 580W panels (2.58 m² each):

System Size	Panels (550W)	Panel Area	Total Roof Area (with 30% setback)
5 kW	10	25.8 m²	36.9 m² (397 sq ft)
8 kW	15	38.7 m²	55.3 m² (595 sq ft)
10 kW	19	49.0 m²	70.0 m² (753 sq ft)
12 kW	22	56.8 m²	81.1 m² (873 sq ft)
15 kW	28	72.2 m²	103.2 m² (1,111 sq ft)
20 kW	37	95.5 m²	136.4 m² (1,468 sq ft)

See our Rooftop Solar Feasibility Checker to verify your specific roof dimensions with actual shading analysis.

Real-World Examples

5 kW System (Typical UK Home)

A typical UK household consuming 4,200 kWh/year needs a ~4.5-5.0 kWp system. With 550W panels: 10 panels (5.50 kWp). String configuration: 5 + 5 on dual MPPT. Roof area needed: ~37 m². Annual generation: ~5,500 kWh (temperate yield of 1,100 kWh/kWp).

10 kW System (Typical US Home)

A US home with 1,250 kWh/month needs ~10 kWp. With 580W panels: 18 panels (10.44 kWp). String configuration: 9 + 9 on dual MPPT. Roof area needed: ~67 m². Annual generation: ~13,800 kWh (temperate yield of 1,320 kWh/kWp).

15 kW System (Australian Large Home)

An Australian home with high air-conditioning load needs ~15 kWp. With 550W panels: 28 panels (15.40 kWp). String configuration: 14 + 14 on dual MPPT. Roof area needed: ~103 m². Annual generation: ~24,000 kWh (subtropical yield of 1,560 kWh/kWp).

Pro Tip: If your roof cannot accommodate the required area, consider switching to higher-wattage panels (e.g., 650W or 700W) to reduce panel count. Alternatively, ground-mount or carport installation can supplement roof space.

Related Guides

Calculate your exact panel count

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How Solar Metrix Pro Helps: The Baseline Generation Profile module in the sidebar above automates all these calculations. Enter your monthly bill and rate in the header and you get your exact system size (kWp), panel count (adjustable wattage), string configuration, and recommended inverter with DC/AC ratio — instantly.
                

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Data sources: NREL PVWatts, Clean Energy Council (Australia), MCS (UK), EIA (US). Panel dimensions based on JinkoSolar Tiger Neo and LONGi Hi-MO X6 series datasheets. Roof area calculations include 30% fire safety setback per IEC 61724 and local fire codes.

Last updated: July 2026 | Browse all guides

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