Can You Have Home Battery Backup Without Solar?
A home battery can be charged entirely from the grid — no solar panels required. Here is when that makes financial sense and what the limits are.
A home battery does not need solar panels to function. A grid-only battery charges from your electricity retailer during off-peak periods and discharges when you need it. The question is whether the economics work — and the answer depends heavily on your tariff structure.
Two Reasons to Install Battery Without Solar
- Energy arbitrage — charge at off-peak rates (10–15c/kWh overnight), discharge at peak rates (40–60c/kWh in the evening), capturing the rate spread as savings
- Emergency backup — have stored power available during blackouts, particularly for households with medical equipment or frequent outages
Does the Arbitrage Work?
In Australian states with time-of-use tariffs that have large peak/off-peak spreads — particularly South Australia and Victoria — a grid-only battery can generate genuine savings. The key variables are the size of the spread between your peak and off-peak rates, your battery's round-trip efficiency (typically 90–95%), and the battery's upfront cost.
| Retailer type | Off-peak rate | Peak rate | Spread | Savings potential |
|---|---|---|---|---|
| Standard flat tariff | N/A | 28c/kWh | None | Nil — arbitrage does not apply |
| Time-of-use | 12–15c/kWh | 40–55c/kWh | 25–40c/kWh | Moderate to good |
| Wholesale pass-through (Amber) | Variable (low overnight) | Variable (high peak) | Large on high-demand days | Strong but volatile |
Backup Without Solar: What to Expect
A battery without solar can only hold the charge it stored before the blackout began. Once that charge is depleted, it cannot recharge until grid power is restored. This is the critical limitation. A solar-plus-battery system can recharge during daylight hours even when the grid is down, giving you indefinite backup in sunny weather.
| Battery size | Average Australian home daily use | Estimated backup duration (essential loads) |
|---|---|---|
| 10 kWh | ~20 kWh/day | 12–24 hours (essentials only) |
| 20 kWh | ~20 kWh/day | 24–48 hours (essentials only) |
| 30 kWh (two batteries) | ~20 kWh/day | 48–72+ hours (essentials only) |
Virtual Power Plants and Grid-Only Batteries
Some Australian VPP operators — including Origin, AGL and Reposit Power — allow grid-only batteries to participate in their programs. Your battery may be dispatched to support the grid during peak demand events, earning you bill credits or cash in return. This additional revenue stream can materially improve the economics of a grid-only installation.
A grid-only battery makes most financial sense with a time-of-use tariff that has a large peak/off-peak spread. On a flat tariff, the arbitrage opportunity disappears and backup power is the only remaining benefit.