How to size your battery (Perth method)

Start with your night-time load. Look at usage between roughly 3pm and 7am. Aim to cover most of it with usable capacity, not all of it.
Add a buffer for degradation. Ten-year warranties often assume some throughput and fade.
Check power, not just energy. Make sure the inverter's continuous power rating can run your real evening loads: air conditioning, induction cooking, the pool pump.
Consider future loads, such as an EV or a heat pump, and the reality of winter PV. Forced charging on a time-of-use tariff can help through gloomy spells.

Simple rules of thumb

8–10 kWh: efficient or compact homes.
10–13.5 kWh: typical 3–4 person households.
15–20 kWh and above: EV households, or homes that want stronger backup.

Cross-check with our calculator, which is DEBS and VPP aware, and confirm your chosen model is CEC-listed. It also needs to be SSL-listed if you want the WA battery rebate.

Where next

Where to place a battery in a Perth home

AS/NZS 5139 clearance rules, garage vs outdoor walls, and what installers check on-site.

How to size a battery for your usage

A step-by-step method covering evening usage and seasonal AC demand.

Synergy Battery Rewards: what the VPP pays

Activation events credit 70¢/kWh on top of DEBS exports, and signing up is a WA rebate condition.

Explore your options

Answer a few questions and see systems and installers that fit your home.