title: "How big should your battery be? A Perth-specific method" description: "Use your night-time load, inverter limits and future plans (EV/hot water) to pick a right-sized battery—without guesswork." lastUpdated: "27 Feb 2026"

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.

title: "How big should your battery be? A Perth-specific method" description: "Use your night-time load, inverter limits and future plans (EV/hot water) to pick a right-sized battery—without guesswork." lastUpdated: "27 Feb 2026"

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.