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A GreenBuildingAdvisor report traced a homeowner’s elevated heat-pump water heater energy use in 2024 and 2025 to more than one likely factor. A household member who preferred baths moved in shortly before consumption rose, while renovation dust dirtied the filter and coil; use returned to normal after that person moved out, but the effects cannot be separated from the available data.
A heat-pump water heater used substantially more electricity in a homeowner’s household during 2024 and 2025, with the rise likely linked to both increased hot-water use and dirt from a basement renovation, according to a GreenBuildingAdvisor report. The writer’s monthly records show consumption rose after a stepson who preferred baths moved in and returned to its usual pattern after he moved out, but the available data cannot establish how much each factor contributed.
The report’s author, building-science consultant Allison A. Bailes III, said the heater’s annual energy use in 2024 was 89% higher than in 2020. Energy use also remained unusually high in 2025. The comparison is specific to Bailes’s home and those calendar years; it is not a general estimate for other households or water heaters.
Bailes initially suspected dust from a basement remodeling project that began in February 2024. Heat-pump water heaters draw heat from surrounding air, and the renovation produced dust and other airborne particles. Bailes reported that the unit was not always covered or turned off, and that its filter was very dirty by January 2025. The coil and other components also needed cleaning.
However, the monthly data point to another change. Energy use began rising in late 2023, before the renovation began, after Bailes’s stepson moved into the home in August 2023. He preferred baths and moved out at the end of July 2025; the water heater’s energy use then returned to its usual range. Bailes cleaned the coil in April 2025, but the largest visible drop in the monthly graph came in July, so the sequence alone does not prove that cleaning caused the decline.
Why Hot-Water Habits Affect Bills
The report illustrates why a rise in a household energy bill may not have a single cause. Hot-water demand can change when household size or bathing habits change, while dust and restricted airflow can affect how a heat-pump water heater operates. A homeowner who attributes the entire increase to equipment condition may miss a change in use; one who blames household demand alone may overlook maintenance needs.
For readers with heat-pump water heaters, the account offers practical checks, not a controlled test or a promise of specific savings. Bailes recommends covering or turning off the unit during dusty work, checking and cleaning its filter, and cleaning the coil and other components when they become dirty. Tracking energy use alongside household changes can help identify when a pattern began, though it cannot by itself determine the exact cause.
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The Timeline Behind the Spike
Bailes said the home’s records showed a regular seasonal pattern from 2020 through mid-2023: roughly 60 kilowatt-hours a month in winter and about 20 to 30 kWh a month in summer. Consumption began climbing near the end of 2023. The stepson moved in that August, and the basement renovation started the following February.
The remodeling added dust to the heater’s intake environment, while the household gained a person who used more hot water for baths. Bailes also noted a countervailing effect: the renovation brought the water heater into fully conditioned basement space. Before winter 2024–25, the basement had not been heated; warmer surrounding air could help the heat-pump unit operate more efficiently. Bailes said that change may have limited winter energy use, complicating any attempt to isolate the renovation’s overall effect.
“The jolt in energy use those two years actually was caused by both things.”
— Allison A. Bailes III, in the GreenBuildingAdvisor report
How Much Each Factor Added
The report does not quantify the separate energy effect of extra baths, the dirty filter, the coil condition, or the warmer basement. It gives energy consumption but not monthly hot-water volumes, so the contributions cannot be calculated from the records described. The timing of the July 2025 drop also does not isolate the effect of coil cleaning, which took place in April.
The figures describe one household and one heat-pump water heater. They do not establish how much energy another unit will use, whether a dirty filter caused a similar increase elsewhere, or what savings a particular maintenance step would produce. The report also gives no equipment test results or controlled comparison with the heater operating under otherwise identical conditions.
Checks Owners Can Make
Bailes’s recommendations are to protect the heater during dusty renovation work, inspect and clean its filter regularly, and clean the heat-pump coil and other components when dirty. Homeowners can also compare energy records with changes in household occupancy and hot-water routines, while noting that seasonal patterns affect monthly use.
The report does not announce a further test or a new measurement of the heater. Without monthly hot-water-use data or a controlled assessment, the precise share of the two-year increase attributable to demand versus equipment condition remains unresolved.
Key Questions
What caused the water heater’s energy use to rise?
The report attributes the rise likely to two factors: more hot-water use after a stepson who preferred baths moved in, and dust that dirtied the heat-pump water heater’s filter and coil during a basement renovation. The available records cannot show the exact contribution of each.
How large was the reported increase?
In Bailes’s home, annual water-heater energy use in 2024 was 89% higher than in 2020. That figure applies to the comparison in the report and should not be treated as a typical increase for other homes.
Can a dirty filter affect a heat-pump water heater?
The report says renovation dust made Bailes’s filter very dirty and that the coil and other parts also became dirty. Bailes believed the condition affected energy use, but the article does not quantify the effect or establish a general savings figure from cleaning.
What should an owner check if energy use rises?
Check the unit’s filter and coil for dirt, and consider whether occupancy or hot-water habits have changed. Bailes recommends protecting the heater during dusty work, cleaning the filter as needed, and cleaning the coil and other components when they become dirty.
Source: greenbuildingadvisor.com
