Heat pump water heaters have already shown that they can cut electricity use enough to lower people's energy bills. But can they keep hot water available when the grid goes down?
For one Massachusetts homeowner, that was the key question behind a planned purchase of a 50-gallon hybrid water heater.
Here's what to know
The homeowner took to Reddit's r/HeatPumps forum to ask for advice about their plan.
Because "we overproduce 4,000 kwh a year" from solar, as the homeowner explained, a more efficient water heater looked especially useful since it could help them consume more of their own electricity generation rather than relying on the grid.
The original poster also described their home as having oil heat, an $800 credit from Eversource, "9kw enphase micro inverters solar array," and a "Mitsubishi mini split AC/heat pump."
Backup planning also factored into their decision. The OP wrote: "By using the hybrid hot water heater during an outage, we can keep it on, as it only uses 800 watts on heat pump mode."
Because standard electric resistance water heaters usually need much more power, they can be harder to run on stored backup electricity, making the heat pump variety more attractive.
One commenter noted that their Bradford White unit uses about 0.4 to 0.5 kilowatt-hours in heat pump mode and roughly 4.5 kWh in electric resistance mode, while another commenter said their Bradford White "doesn't get above 0.5kWh." The OP added that they import electricity at 19 cents per kilowatt-hour.
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More background
Heat pump water heaters stand out to homeowners looking to electrify without driving utility bills higher. Instead of creating heat the way a conventional tank does, they move heat, which can sharply reduce the amount of electricity needed for everyday showers, dishes, and laundry.
For this household, fuel prices and solar output also shaped the calculation. The homeowner said they had signed an oil contract at $4.69 per gallon, so moving more water heating to electricity, particularly power from their own solar array, could reduce how much oil they need.
If you're looking to upgrade your water heater, one option worth watching is Cala, which makes smart heat pump water heaters designed to match hot water production more closely to household demand.
Cala's customizable smart heat pump water heaters help homeowners decrease their energy bills by heating water exactly when it's needed. That kind of control can help homes make the most of solar generation, off-peak electricity, or limited stored battery power.
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