What size solar system do you actually need? 6.6kW vs 11kW vs 13.3kW vs 17kW compared

The single most common mistake we see isn't picking the wrong brand of panel — it's sizing the system to what a neighbour installed, or to a number a salesperson threw out, instead of to actual household usage. Here's exactly how our four standard sizes compare, using the same numbers our own online quote builder uses to make a recommendation.

6.6kW — the most popular size

• Best for: under 20kWh/day usage — a small home, 1–2 people, minimal air conditioning.
• 14 × 475W panels, $6,500–$9,000 installed after the federal STC rebate.
• Typical savings: $1,800–$2,400/yr.
• A 16kWh GoodWe ESA battery comfortably covers most evenings at this usage level.

11kW — the 4-bedroom family standard

• Best for: 20–40kWh/day usage — an average family, 3–4 people, regular air conditioning.
• 23 × 475W panels, $10,500–$14,000 installed.
• Typical savings: $2,800–$3,800/yr.
• A 16kWh GoodWe ESA suits this usage well.

13.3kW — large family, ducted A/C or a pool

• Best for: 40–60kWh/day usage — a large family home running ducted air conditioning, a pool, or a workshop.
• 28 × 475W panels, $12,500–$16,000 installed.
• Typical savings: $3,800–$5,200/yr.
• We'd recommend 16–32kWh of battery storage at this size.

17kW — large modern home

• Best for: 60+kWh/day usage — a large modern home with a pool and ducted reverse-cycle air conditioning.
• 36 × 475W panels, $15,000–$19,000 installed.
• Typical savings: $5,000–$7,500/yr.
• At this size we require a battery (32kWh+) as part of the system — usage this high needs somewhere for the excess daytime generation to go.

How to actually tell which one's yours

Grab a recent electricity bill and find the total kWh used over the billing period, then divide by the number of days in it — that gives you kWh/day, which is exactly what sorts you into one of the four bands above. It's a five-minute exercise that beats guessing from a neighbour's roof every time, since two houses on the same street can have completely different usage depending on pool pumps, ducted A/C, EV charging or just how many people live there.

Don't want to do the maths yourself?

Our free home energy audit or Quote Builder does this sizing for you — tell us your usage (or upload a bill) and we'll recommend the right size with a savings estimate, the same way the numbers above were generated. Final sizing is always confirmed on a site visit, since roof space, shading and phase supply can shift the recommendation either way.

Call Brooke on 0408 258 298, or use our Quote Builder to get your exact number.