Midday Saver + battery Perth: how to use off-peak charging to cut your power bill

Synergy's Midday Saver tariff has a wide gap between its cheapest and most expensive hours: about 24.34c/kWh overnight, and 55.33c/kWh in the 3pm-9pm peak. A home battery can work that gap on its own, without any solar panels involved. Charge overnight, discharge into the peak, and you pocket roughly 31c for every kilowatt-hour you cycle, before round-trip losses.

For a typical 10kWh battery doing that once a day, it works out to about $628 a year in pure arbitrage savings on Midday Saver, on top of anything solar adds. This guide walks through the rate structure, the daily cycle, the real annual numbers, and how Midday Saver stacks up against the flat A1 tariff once a battery is in the mix.

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What are Synergy's Midday Saver rates from 1 July 2026?

The key spread for battery arbitrage: charge at 24.34c overnight, discharge at 55.33c during peak = 31c/kWh spread.

Always confirm current Midday Saver rates at synergy.net.au, rates are subject to change.

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How does the battery arbitrage actually work?

A Perth home on Midday Saver with a battery follows this daily cycle:

Night (9pm-9am): Grid charges the battery at 24.34c/kWh. Battery fills to 90-100% state of charge by morning.

Day (9am-3pm): Solar panels generate at near-zero cost, since the panels are already paid for. The household covers its own loads with that solar during super off-peak hours: any grid import in this window is cheap, at 8.85c. Excess solar tops up the battery if it isn't already full.

Late afternoon and evening (3pm-9pm peak): Battery discharges to cover household loads. Grid purchases avoided at 55.33c.

Net saving per kWh discharged during peak: the 31c/kWh spread, minus round-trip efficiency losses of about 10%, comes out to roughly 28c net saving per kilowatt-hour cycled.

No solar panels? You can do even better. Without panels competing for battery capacity, you don't have to charge overnight at 24.34c. Charging from the grid during the 9am-3pm super off-peak window instead, then discharging into the 3pm-9pm peak, widens the spread to about 46c/kWh (55.33c peak minus 8.85c super off-peak) before losses. The catch is timing: your battery management system needs to finish charging by 3pm rather than trickling in overnight, so check what your system supports.

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How much can a battery save you on Midday Saver each year?

Assumption: the battery cycles once a day on average, some days partial, some days a full cycle. 250 full cycles a year is a reasonable Perth estimate.

For a walkthrough on choosing the right capacity for your own evening load, see how to size a home battery for Perth.

Note: this is the grid arbitrage saving only, the difference between charging cost and discharge value. On top of it, the battery also captures solar generation during the day that would otherwise export under Perth's DEBS export scheme at 2c/kWh, adding further self-consumption value at the peak rate.

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What changes if you also have solar panels?

With solar panels and a battery on Midday Saver:

1. Solar covers daytime loads at close to zero effective cost, since the sunlight is free once the panels are paid off, displacing 8.85c off-peak imports.
2. Solar overproduction tops up the battery during the day (9am-3pm super off-peak), so you may not need the overnight grid-charge at all.
3. Battery discharges during the 3pm-9pm peak at 55.33c value.
4. On cloudy days, the battery falls back to charging overnight at 24.34c to cover the peak.

The super off-peak 8.85c rate is Synergy's cheapest import rate. If your solar is generating well during 9am-3pm, most of your consumption in that window gets covered by panels, meaning virtually no grid import at any time of day on good solar days.

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Is Midday Saver or A1 better with a battery?

Without a battery, Midday Saver suits households that naturally use less power during the 3pm-9pm peak. With a battery, the picture changes: the battery shifts consumption out of the peak regardless of your natural usage pattern.

Here are the two tariffs compared on the same basis, a 10kWh battery with 9kWh usable capacity, 250 cycles a year:

On the numbers alone, the two are close, and A1 is marginally ahead when you're comparing grid arbitrage in isolation. But the Midday Saver figure only counts the overnight arbitrage. It leaves out what a Midday Saver battery does with solar: any excess solar sent to the battery during the 9am-3pm super off-peak window and discharged into the 55.33c peak is worth 55.33c a kilowatt-hour, not the 2c/kWh it would otherwise earn as an export. On A1, solar self-consumption is worth the same flat 33.26c whether it happens at 10am or 7pm, so there's no equivalent uplift.

For a household with solar and evening-heavy loads, aircon, cooking, an EV charging after dark, that extra solar-to-peak value usually tips the total in Midday Saver's favour. For a battery running on grid arbitrage alone, with no solar, the two tariffs land close to even, and the better pick depends on how much of your evening load the battery can cover before the peak window ends. Model your own usage before switching: our full A1 vs Midday Saver comparison walks through the break-even calculation.

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Who benefits most from Midday Saver with a battery?

Highest benefit on Midday Saver + battery:

• Households with high evening consumption (aircon, cooking, TV, hot showers) in the 3pm-9pm peak
• Two-income households who are away during the day: low daytime consumption, high evening use
• Households with EVs that can be programmed to charge during the 9pm-9am off-peak window, at 24.34c instead of 55.33c on the Midday Saver peak
• Any household where the battery can reliably cover 3pm-9pm loads from solar generation or an overnight charge

Lower benefit on Midday Saver + battery:

• Households that already shift most consumption to midday naturally, with few evening loads
• Households where battery capacity is undersized relative to evening loads, so the battery is depleted before 9pm and still buying at 55.33c

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How do you set up a battery for Midday Saver?

Configure the battery schedule: Most battery management systems (Sungrow iSolarCloud, Fronius Solar.web, Tesla app) let you set:

• Charge window: 9pm-6am (using overnight off-peak at 24.34c)
• Discharge window: 3pm-9pm (peak window)
• Battery reserve for backup: 10-20%, in case of overnight grid disruption

Monitor peak consumption: In the first month after switching, track your Synergy usage (via myaccount.synergy.net.au) to verify the battery is covering enough of the 3pm-9pm peak to justify the higher supply charge: $1.33/day versus $1.19/day on A1, about $49 a year more.

EV charging setup: If you have an EV, configure charging to the 9pm-9am window (24.34c on Midday Saver versus 55.33c if you charge at 6pm). An EV charging 15kWh a night at 24.34c costs $3.65 a charge. At the Midday Saver peak rate that would be $8.30 a charge. Overnight scheduling saves $4.65 a charge. For the full picture on EV tariffs and smart charging strategies in WA, see electric vehicle charging at home: WA tariffs, costs, and smart strategies.

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Midday Saver's 31c spread between off-peak and peak rates is the biggest tariff arbitrage available to Perth battery owners today. Add solar to the mix, and it usually beats A1 for households with evening-heavy loads. Still, run your own numbers before switching: working out whether Midday Saver is worth it for your home covers the break-even calculation, and the answer depends on how well your battery covers your natural 3pm-9pm peak.