Bill size, roof orientation and battery choice all matter. Here's a plain-English sizing guide for typical Perth households — and why 6.6 kW is no longer the default.
The old "6.6 kW standard" is outdated
With Synergy's DEBS export tariff at just 2c/kWh off-peak, the game has shifted from export as much as possible to self-consume as much as possible. That means bigger systems paired with batteries.
Quick sizing table
| Quarterly bill | Recommended system | Battery |
|---|---|---|
| < $400 | 6.6 kW | Optional |
| $400 – $700 | 10 kW | 10 kWh |
| $700 – $1,100 | 13.3 kW | 13.5 kWh |
| $1,100+ | 15–20 kW | 20+ kWh |
Why size up?
- Panels are the cheapest part. Going from 6.6 → 10 kW adds only ~$2,500 but roughly doubles winter output.
- EVs are coming. A 15 kWh/day EV adds ~$1,600/yr to your bill unless solar covers it.
- Air-con load. Perth summers routinely push 8–12 kWh/day just in cooling.
Orientation still matters
- North: peak midday production — best for battery charging
- West: afternoon peak — great for air-con offset
- Split N/W: the sweet spot for most Perth homes
Get a free custom quote
Our team will pull your actual usage data from Synergy and design a system that matches — not a one-size-fits-all package.
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