Tariffs
When should you force-charge a home battery?
Forced-charging means telling your battery to fill up from the grid at a set time, instead of waiting for solar. Done in the cheap window, it saves you buying power at the evening peak.
The short answer
- Best time to charge
- ~8.9c/kWh
- 9am to 3pm on Midday Saver
- Never charge
- ~55.3c/kWh
- 3pm to 9pm, the evening peak
- You save, per kWh
- ~46c
- Charging 9am to 3pm instead of buying at peak
When does it actually pay off?
It only earns its keep in a narrow set of conditions. Check both lists.
Worth it when
- It's winter or heavily overcastSolar falls short of what the battery needs for the evening, so it's half-empty by dinner.
- You're on a time-of-use planYou need a real gap between a cheap window and the peak for this to work.
- Your evening use is predictableDinner, heating or an EV charge. Top up ahead of time instead of buying at peak.
Not worth it when
- You're on flat A1Every hour costs the same (~33.3c), so there's no cheap window. A1 customers get nothing from this.
- It's spring or summerRarely worth it once spring solar returns and the battery fills itself most days.
On A1? See A1 vs time-of-use tariffs for batteries for the plan comparison.
What counts as forced-charging?
A normal day
Solar charges the batterythenBattery runs the evening
The battery charges from your own panels during the day and discharges in the evening.
A forced-charging day
Grid charges the battery at a set timethenFull before the peak
The inverter draws from the grid during a set window, whatever your panels are doing. The battery is topped up before the evening peak arrives.
Why the 9am to 3pm window specifically?
Midday Saver splits the day into three prices. 9am to 3pm is cheapest because rooftop solar floods the grid across WA then. It's cheap even if your own panels aren't producing that day.
| Price band | Time | Price (2026) | For forced-charging |
|---|---|---|---|
| Super off-peakThe solar-soak window | 9am to 3pm | ~8.9c | Best |
| Off-peakOvernight | 9pm to 9am | ~24.3c | Distant 2nd choice |
| PeakEvening | 3pm to 9pm | ~55.3c | Avoid |
Prices per kWh, incl. GST, rounded. Source: Synergy's published price list, via our tariff data.
What 1 kWh in the battery costs you
- Charged 9am to 3pm~8.9c
- Charged overnight~24.3c
- Bought at the evening peak instead~55.3c
The midday price is about 16% of the peak. Use overnight off-peak only if the midday window isn't practical for your setup.
How do you set up forced-charging?
Six steps, in order. Your installer can do most of this in your inverter or monitoring app.
Confirm your tariff
On A1? Stop hereIt only pays off on a time-of-use plan like Midday Saver. On flat A1, skip this entirely.
Set a backup reserve
If backup power matters to you, set a minimum state of charge so the battery never sits fully empty.Schedule the charge window
Match the cheapest band in your inverter or monitoring app: 9am to 3pm on Midday Saver.Only charge what you'll use tonight
Cap the charge to imports you'd otherwise pay for. Over-filling adds cost without adding coverage.Check your VPP rules first
Can override your scheduleSome programs set their own rules for when and how you can charge or discharge, and those can override your own schedule.
Re-check each season
Once longer days bring solar back up, you likely don't need forced-charging at all.
Does a VPP change any of this?
Talk to your installer first
Terms on this page
- Time-of-use plan
- A plan where the price changes with the time of day. Synergy's Midday Saver is one.
- Peak
- 3pm to 9pm, the most expensive time to buy power on Midday Saver.
- State of charge
- How full the battery is, as a percentage.
- VPP
- A virtual power plant. Your battery joins a program that can use it during grid events, and you're usually paid or credited for it.