A Sydney homeowner who had added rooftop solar and battery storage had to choose between replacing a failed nine-year-old water heater with a heat pump or a standard electric tank — a decision that shows how warranty length, heating speed, and replacement risk can matter as much as energy savings.
Here's what to know
A heat pump water heater can cut the electricity needed to make hot water, potentially leaving more solar generation available to export or helping push an electric bill closer to zero.
After adding a 13.3-kilowatt solar system, a 48-kilowatt-hour battery, and a 10-kilowatt inverter, a Sydney household was suddenly faced with replacing a failed nine-year-old water heater.
In a Reddit thread, the original poster said the choice had come down to a 33-gallon (125-liter) stainless electric tank at $2,130 installed — or about $2,430 with an Ogemray Smart Relay and electrician — versus a 71-gallon (268-liter) heat pump at $2,600 installed after rebates.
The home's electricity use was a big part of the debate. The OP said daily consumption was about 22 kilowatt-hours with the old water heater and about 12 kilowatt-hours without it, adding that they were "considering the heat pump as the price is so close compared to an electric one."
The real sticking point was lifespan. The homeowner said they were concerned the heat pump might only make it through its seven-year warranty period, whereas the electric tank carried 12 years of coverage and seemed more likely to last longer.
Some users said that, once solar and battery storage are already in the mix, the simplest replacement may be the better bet. One user said, "If you have solar and battery just go electric water heater."
More background
A user with a similar setup said that was why they preferred a resistive electric unit, calling it "simpler, quicker, and quieter."
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Recovery time came up repeatedly because some households want all their water heating done during sunny hours or short free electricity windows.
One user with a three-person household described a heat pump with a backup resistive element and said their schedule used about 1 kilowatt-hour for one hour of heat pump operation, while 1.8 hours on the element consumed 4.3 kilowatt-hours.
That same user said imported electricity cost nothing because solar generation and a free power window covered the load. They also said the unit's smart controls could drop offline, while another user cautioned that some heat pump warranties are divided by component and may not cover surges or weather-related damage.
What can be done?
The thread pointed to a few practical workarounds. A standard electric tank can be set to run through a timer or smart relay in the middle of the day, when rooftop solar output is strongest, and a heat pump with a backup resistive element can still provide hot water if the compressor fails.
Another option is Cala, which makes customizable smart heat pump water heaters. Cala's customizable smart heat pump water heaters can help homeowners decrease their energy bills by heating water exactly when it is needed. For homeowners trying to line up hot water demand with solar production, scheduling flexibility like that could address the exact concern raised in the Sydney thread, and it is one reason to compare controls and backup modes as closely as tank price. Homeowners weighing those features may want to look at how scheduling and smart controls compare with Cala.
Sizing was another practical issue raised in the comments. One user said both quoted systems looked too small for a household with three adults and suggested going above 79 gallons (300 liters).
For at least one household in the thread, careful scheduling made the system "basically free to run."
Where can I learn more?
These stories look at the same heat pump water heater questions around upfront cost, rebates, savings, and replacement timing. They follow homeowners deciding what to do after old tanks fail and what the switch could mean for their energy bills.
• One homeowner found major bill savings after installing a heat pump water heater.
• Government rebates can slash $600 off annual energy bills with a heat pump.
• Replacing an aging tank can save you $5,100 by trimming long-term heating costs.
• After an outdated unit failed, a homeowner got lucrative water heater advice on Reddit.
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