Summary (for skimmers)
If you want blackout backup, your battery needs a **reserve** (a minimum state-of-charge it won’t discharge below). Set it wrong and you’ll either:
- run out of backup during outages, or
- sacrifice too much bill savings.
This guide explains the reserve concept, common reserve levels, and how VPP programs can change the rules.
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What is a “battery reserve”?
Battery reserve is the chunk of capacity you keep in the tank for emergencies.
Example: a 10 kWh battery with a 20% reserve keeps ~2 kWh for backup and uses ~8 kWh for daily savings (roughly — usable capacity varies).
Why reserve settings matter more in 2026
Two reasons:
1) More households are buying batteries for **both** savings and resilience.
2) VPPs and dynamic tariffs make the “optimal” discharge behaviour more complex.
Common reserve levels (rule of thumb)
There’s no perfect number, but these are common patterns:
- **0–10%** reserve: maximise bill savings (minimal backup)
- **20–30%** reserve: balanced for most homes
- **40–60%** reserve: higher resilience focus (less savings)
What should drive your choice:
- outage frequency in your area
- whether you need to run critical loads (fridge, lights, internet)
- whether you have EV charging or large evening loads
Reserve + blackout backup hardware (don’t miss this)
A reserve setting alone isn’t always enough. Some systems require:
- a backup box / gateway
- changeover switch / critical loads sub-board
Ask the installer to specify (in writing):
- what circuits are backed up
- what the battery can actually power during an outage
How VPPs interact with reserve
Good VPPs let you set a minimum reserve and respect it.
Before joining, confirm:
- can the VPP export your battery below your reserve?
- can you opt out on high-demand days?
- any minimum term or exit fee?
Practical setup checklist
1) Decide “critical loads” you actually care about
2) Set reserve (start at 20–30% for most homes)
3) Run 2–4 weeks of real usage, then tune
4) If joining a VPP, confirm reserve/override settings first
Internal links (ABQ)
- Get 3 free quotes: https://australianbatteryquotes.com.au/
- VPP guide: https://australianbatteryquotes.com.au/vpp-australia-2026-guide/
- Cost benchmark: https://australianbatteryquotes.com.au/how-much-does-a-10kwh-battery-cost-in-australia-real-2026-pricing-rebates/
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