The panel count that's right for your home comes from your quarterly bill, not from copying a neighbour's system. Using the mainstream 440 W panel, here's what each of our recommended system sizes needs:
| Quarterly bill | System size | Panels (440 W) | Inverter |
|---|---|---|---|
| Under $300 / quarter | 5 kW | 11 | 5 kW |
| $250-$500 / quarter | 6 kW | 14 | 5 kW |
| $300-$600 / quarter | 6.6 kW | 15 | 5 kW |
| $500-$800 / quarter | 8 kW | 18 | 6 kW |
| $700-$1,000 / quarter | 10 kW | 23 | 8.2 kW |
| $900+ / quarter | 13.2 kW | 30 | 10 kW |
| $1,000+ / quarter | 15 kW | 34 | 12 kW |
| $1,400+ / quarter | 20 kW | 45 | 15 kW |
The usual starting point
On a $300-$600 quarterly bill the answer is the 6.6 kW system at 15 panels. 6.6 kW of panels on a 5 kW inverter uses the full 133% oversizing allowance: you claim STCs on 6.6 kW while the inverter, and the network approval, stay at 5 kW.
Bigger or smaller than the table?
Two things move the count away from the bill-based default: roof space (across our size range, each panel works out to about 2.2 m² of roof including gaps and rails) and future load, if an EV or a heat pump is coming, size up a step now rather than adding a second array later. See full pricing, generation and battery pairing for every size on /solar-systems/.
Common questions
How many panels for a 6.6 kW system?
15 panels at 440 W, on a 5 kW inverter.
How many panels for a 10 kW system?
23 panels at 440 W, on a 8.2 kW inverter.
How do I work out how many panels I need?
Start from your quarterly bill, not a target kW. Under $300 / quarter typically suits a 5 kW system, $300-$600 / quarter suits 6.6 kW, and $700-$1,000 / quarter usually justifies 10 kW or more, see the table above for the exact panel counts.