Solar Sponge tariff in Perth: is it better than Midday Saver?

Short answer: yes, effectively. Synergy's Midday Saver tariff already gives Perth solar households a Solar Sponge style rate, a cheap window from 9am to 3pm when rooftop solar is flooding the grid. WA doesn't run a separate government Solar Sponge product on top of it. Midday Saver's super off-peak band is doing that job right now.

If you've got solar and a smart meter, Midday Saver is the closest thing Perth has to South Australia's Solar Sponge tariffs. Here's how it works, what's genuinely cheap about it, and whether a lower future rate would move the needle much.

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What is a Solar Sponge tariff?

"Solar Sponge" isn't a brand name. It's a category: a tariff that sets a very low, or even zero, electricity price during the hours when the grid is swimming in solar generation. Low enough to nudge households into using more power right when the grid needs it used.

The idea started in South Australia, where negative wholesale electricity prices at midday on sunny days are common.

The problem it solves: when rooftop solar across a whole state generates more than the grid needs, something has to give. Excess generation gets curtailed (switched off at the inverter), or grid frequency climbs toward unsafe territory. A Solar Sponge tariff takes the cheaper path: instead of throttling solar, it pays households to soak up the extra power. Run the dishwasher. Charge the EV. Heat the pool. All during the oversupply window, not the evening peak.

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Is Midday Saver WA's Solar Sponge tariff?

Yes. Synergy's Midday Saver plan is WA's version of it:

• Super off-peak: 8.85c/kWh, 9am to 3pm. This is the window that lines up with Perth's peak solar generation hours.
• Peak: 55.33c/kWh, 3pm to 9pm.
• Off-peak: 24.34c/kWh, the remaining hours.

At 8.85c/kWh, the super off-peak rate is the cheapest scheduled time-of-use import rate on offer to Perth solar households. That's Solar Sponge pricing in practice, no separate product required.

One naming trap worth clearing up: Midday Saver is sometimes lumped together with Synergy's separate Smart Home plan. They're different products with different rate structures, and mixing them up leads to comparing the wrong numbers. If you want the details on how Smart Home works, our Synergy Smart Home plan guide breaks down who it suits.

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Is WA trialling a separate Solar Sponge rate?

The WA Government and the Economic Regulation Authority (ERA) have flagged further tariff reform as part of the state's Energy Transformation Strategy. On the table:

1. Deeper price cuts during midday solar oversupply
2. Variable, real-time pricing that moves with grid conditions
3. Compensation mechanisms for households that actively help balance the grid

None of that has landed as a live product yet. Midday Saver remains the main time-of-use tariff available to Perth residential solar households, and Synergy is currently the only residential electricity retailer serving standard customers in the South West Interconnected System.

Keep an eye on announcements from Synergy, the WA Government's Energy Division, and the ERA if you want to catch a new product the day it lands. For the long view on how Perth's rates got here, our history of Synergy's electricity prices since 2007 is worth a read.

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What if WA introduces a lower Solar Sponge rate?

Say WA rolled out a 0c or 2c midday rate, closer to South Australia's. Would it change much for you? Depends on whether the lower midday rate outweighs a higher peak rate elsewhere.

For most Perth solar households, the answer is: not as much as you'd think. Solar generation already peaks during 9am to 3pm, the same window Midday Saver's super off-peak rate covers. Households are largely self-consuming their own solar during that time, not importing from the grid. Dropping the import rate from 8.85c to 0c/kWh mostly saves you money on power you weren't buying anyway.

The bigger lever on Midday Saver is the 55.33c/kWh peak rate from 3pm to 9pm. Avoiding that, through battery storage or shifting load later in the day, is where the real savings sit. Our guide to Midday Saver battery arbitrage walks through the actual annual numbers.

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Who benefits most from Solar Sponge pricing?

Pool owners. A pump timed to run 9am to 3pm burns cheap midday electricity by default. A lower midday rate would only sweeten that further.

EV owners charging at home. 8.85c/kWh during the day versus 55.33c/kWh in the evening is a large gap, and it compounds fast over a full battery charge. Our guide to EV charging costs and tariffs in WA covers how to schedule daytime charging around it.

Heat pump hot water systems. Set the timer for 9am to 2pm and the tank heats on cheap midday power, sometimes straight off solar, ready for the day's hot water demand.

Anyone with flexible loads. Dishwashing, laundry, anything that doesn't need to happen right now: shift it into the 9am to 3pm window and Solar Sponge pricing works in your favour.

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What should you do now?

Don't wait on a hypothetical future product. Optimise against Midday Saver today:

1. Switch to Midday Saver if you've got a smart meter and solar, or heavy daytime usage. Our switching guide walks through eligibility and the break-even math.
2. Time your appliances to the 9am to 3pm window: washing machines, dishwashers, pool pumps, hot water systems.
3. Add a battery to bank solar surplus for the evening peak, displacing that 55.33c/kWh import rate.
4. Consider daytime EV charging if you're weighing up an EV: it's one of the biggest single levers on a Midday Saver bill.

These moves pay off regardless of what WA does next on tariff reform. And if a cheaper midday rate does eventually arrive, a household already set up for daytime consumption will feel the benefit immediately, no re-learning required. If you're still deciding between Midday Saver and the standard A1 tariff, our full comparison lays out the real scenarios and where the break-even falls.