Your home-use buffer is the part of your battery SmartShift won't sell to the grid, so there's enough left to run your home through the expensive evening hours. Your home still uses it as normal, so it's fine to see it run down overnight. SmartShift trades everything above it.
What we recommend
From our data, this is what homes with a battery your size typically use in the evening, between 4 and 9pm when prices are highest. Yours will depend on your household, so adjust to fit.
| Battery size | Average home use | % of battery size |
|---|---|---|
| Under 10 kWh | ~3.5 kWh | 40% |
| 10 to 15 kWh | ~4.5 kWh | 35% |
| 15 to 20 kWh | ~5 kWh | 30% |
| 20 to 25 kWh | ~6 kWh | 28% |
| 25 to 30 kWh | ~6.5 kWh | 25% |
| 30 to 40 kWh | ~7.5 kWh | 23% |
| 40 kWh and over | ~8.5 kWh | 20% |
Why the evening
On wholesale prices, power is cheapest in the middle of the day, when solar floods the grid, and most expensive in the evening, roughly 4 to 9pm, when the sun drops and everyone's home. Your home-use buffer should cover that evening peak, so you can run on your own battery instead of buying at the highest prices. You can set more if you want to keep extra in reserve overnight.
Sources: AER: State of the Energy Market 2025, Ch.2 · AEMO Quarterly Energy Dynamics
When to set more or less
Higher if you run heating or cooling in the evening, have a big household, or cook a lot. Cold southern winters push evening use up too.
Lower if you cook with gas, keep evenings light, or want to free up more of your battery for SmartShift to earn with.
Big one-off loads like EV charging, a pool or electric hot water are far larger than everyday use, and are usually cheaper to run from midday solar or cheap grid power than to hold battery back for. We'd leave them out of your buffer.
Further reading: energy.gov.au: appliances and running costs
3 things worth knowing
It's meant to run down. SmartShift won't sell below your buffer, but your home keeps using it through the evening, so seeing it drop is normal.
It's separate from your outage reserve. Your outage reserve stays locked for blackouts. Your home-use buffer sits on top of it, for everyday use.
More buffer means less earning. The evening is both when you most want power from your battery and when it's worth the most to sell. The best setting is the smallest buffer that still gets you through the evening comfortably. You can change it any time.
Recommendations are based on how Amber battery customers use their batteries across the 4 to 9pm evening, measured from our own fleet. Price information is based on AEMO and AER market data. Your own use depends on your home, your appliances and the season.
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