When should you force-charge a home battery?

Forced-charging means telling your battery to pull power from the grid on a schedule, instead of waiting for solar to fill it. It's worth switching on when winter cloud or short days leave your battery half-empty by evening, so you'd otherwise be buying at peak rates to cover dinner and the evening load.

The window matters as much as the decision. On Synergy's Midday Saver plan, the cheapest band is 9am-3pm, priced well under a third of the 3pm-9pm peak rate. Schedule the charge there and you buy cheap instead of dear. On a flat A1 plan, every hour costs the same, so there's no cheap window to force-charge into. A1 customers get nothing from this strategy: see A1 vs time-of-use tariffs for batteries for the plan comparison.

What counts as forced-charging?

A normal battery charges from your own solar during the day and discharges in the evening. Forced-charging overrides that: the inverter draws from the grid during a set window regardless of what your panels are doing, topping the battery up before the evening peak arrives.

When does it actually pay off?

Forced-charging earns its keep in a narrow set of conditions:

• Winter or heavily overcast days, when solar generation falls short of what the battery needs to cover the evening.
• Time-of-use plans only. You need a real gap between a cheap import window and the peak window for the arbitrage to work.
• A predictable evening load. If you know you'll draw down the battery for dinner, heating, or an EV charge, topping up ahead of time avoids importing at peak rates instead.

It doesn't pay off on a flat-rate plan, and it's rarely worth it once spring solar returns and the battery fills itself most days.

Why the 9am-3pm window specifically?

Synergy's Midday Saver plan splits the day into three price bands. The 9am-3pm band is priced lowest because that's when rooftop solar floods the grid statewide, so retail rates drop to encourage daytime use, whether or not your own panels are producing that day.

Charging in the 9am-3pm window costs a fraction of charging at peak. The overnight off-peak band is a distant second choice if the midday window isn't practical for your setup.

How do you set up forced-charging?

1. Confirm your tariff. Forced-charging only pays off on a time-of-use plan like Midday Saver. On flat A1, skip this entirely.
2. Set a minimum state of charge if backup power matters to you, so the battery never sits fully empty.
3. Schedule the charge window in your inverter or monitoring app to match the cheapest tariff band (9am-3pm on Midday Saver).
4. Cap the charge to avoidable imports. Don't fill capacity you won't use that evening; over-filling just adds cost without adding coverage.
5. Check any VPP program constraints first. Some programs set their own rules for when and how you can charge or discharge, and those can override your own schedule.
6. Re-check the schedule each season. Once longer days bring solar generation back up, you likely don't need forced-charging at all.

Does a VPP change any of this?

If you're enrolled in a VPP, talk to your installer before setting a forced-charge schedule. VPP programs can define their own charge and discharge windows, and those take priority over a manual schedule. See is a VPP right for you? for a framework to weigh that trade-off.

Where next

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.

A1 vs Midday Saver with a battery

How each tariff changes battery savings, including forced charging in winter.

WA battery rebate: are you eligible?

Synergy customers get $130/kWh back, capped at $1,300.

Explore your options

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