A Southern California plumber took to Reddit to share how heat pump water heaters are impacting their customers' utility bills. 

In the post to r/heatpumps, the user shared data showing annual savings of about $370 after the upgrade.

The plumber posted billing data from a three-person Southern California household that replaced a 30-gallon gas tank water heater from 1991 with a 65-gallon hybrid heat pump water heater at the end of 2025. 

The homeowner had to extrapolate data over the same December-to-March period between their old unit and new unit, as they had only had the new one for that long, since December 2025. They said the old gas water heater averaged 29.75 therms a month in winter, translating to about $54 per month and roughly $650 annually on the homeowner's utility bills. 

The new heat pump water heater averaged 40.1 kilowatt-hours of electricity a month, for an estimated cost of about $24 monthly and extrapolating to roughly $283 per year. That put the estimated annual savings at $370.92.

The extrapolation involves a colder time of year, but as water heaters remain indoors, the surrounding heat does not change as much as outdoor temperatures, especially in California, though it's likely that both the gas and heat pump models would be using slightly less energy to heat the water during the summer.

Fortunately, savings like these are not uncommon for homeowners who switch to heat pump water heaters. Rather than generating heat directly, these systems use refrigerant and compression technology to move heat, making them far more efficient than traditional models.

That efficiency can add up to significant savings quickly. Cala estimates that homeowners who replace a standard electric water heater with one of its modern heat pump models could save more than $9,850 on utility bills over 10 years.

Water heating is one of the biggest energy costs in many homes, and a more efficient system can trim bills month after month, especially if it replaces an older, undersized, or poorly performing unit.

Heat pump water heaters are drawing more attention because they can reduce energy use while still delivering more than enough hot water for your needs. 

It can also make an all-electric home easier to live in. Efficient electric appliances can pair well with rooftop solar, helping homeowners push utility costs even lower and depend less on gas.

Whether a heat pump water heater makes sense depends on current fuel costs, the age of your existing water heater, your utility's electric rates, and local rebates. 

As the original poster summed it up, "Your results will depend mainly on: your hot water usage habits [and] your utility rates."

If this has you curious about how much a heat pump water heater could save you on monthly costs, connect with the experts at Cala. 

Cala specializes in customizable smart water heaters that help homeowners decrease their energy bills by learning your home's habits and delivering hot water exactly when it's needed. 

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