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A GreenBuildingAdvisor report traced a homeowner’s unusually high heat-pump water heater energy use in 2024 and 2025 to a combination of increased hot-water demand and dirty equipment. The data do not establish how much each factor contributed, but usage returned to normal after the additional household member moved out.
A homeowner’s heat-pump water heater used substantially more energy in 2024 and 2025, and a GreenBuildingAdvisor report attributes the rise to a combination of increased hot-water use and dust that dirtied the unit’s filter and coil. Energy use returned to its usual range after a family member who preferred baths moved out, though the report says the two causes cannot be separated precisely.
The author, building-science consultant Allison A. Bailes III, tracked the home’s energy use and reported that the water heater’s annual consumption in 2024 was 89% higher than in 2020. Consumption remained abnormally high in 2025. The figure for 2026 in the report includes an estimate for the final four months of that year, so it is not a full-year measured total.
Bailes initially suspected dust from a basement renovation that began in February 2024. He said he had not always covered or turned off the water heater during the work, which filled the area with dust and other particles. A photograph showed a heavily soiled filter. He also cleaned the unit’s coil in April 2025; monthly consumption fell sharply in July, a pattern that appeared to support the equipment-maintenance explanation.
But the monthly data pointed to another factor: consumption began rising steeply at the end of 2023, before the renovation started. Bailes said his stepson moved into the home in August 2023, preferred baths to showers, and stayed until the end of July 2025. Energy use returned to its usual range after he moved out. Bailes concluded that both added hot-water demand and dirty components contributed, while noting that he lacked monthly hot-water-use data to calculate each factor’s share.
Demand and Maintenance Both Matter
The report shows why a higher utility bill may not point to a single equipment fault. A heat-pump water heater can use more electricity when household hot-water demand rises, and its performance may also suffer when dust blocks the filter or coats the coil. In this case, both conditions occurred during the same period, so the annual energy totals alone could not identify one definitive cause.
That distinction matters for homeowners deciding what to check. Cleaning a filter may help a dirty unit, but it will not explain a sustained increase caused by more baths or other hot-water use. Conversely, assuming the rise is only due to household habits could overlook an equipment issue. Tracking energy use alongside occupancy, water use, and maintenance can help narrow down the explanation.
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A Renovation Overlapped With Higher Use
Bailes described relatively regular monthly use from 2020 through the middle of 2023: around 60 kilowatt-hours (kWh) per month in winter and roughly 20 to 30 kWh per month in summer. Those figures are observations from this one household, not a benchmark for all heat-pump water heaters; household size, climate, settings, and hot-water habits vary.
The timing is central to the report’s conclusion. The rise began in late 2023, after the stepson moved in but before the basement renovation began in February 2024. Renovation dust plausibly worsened the unit’s condition, while the additional occupant increased hot-water demand. The basement work also brought a change that could improve performance: Bailes said it moved the water heater into fully conditioned space. Before the winter of 2024–25, the basement was unheated, and warmer surrounding air may have helped offset some of the extra energy use.
“The jolt in energy use those two years actually was caused by both things.”
— Allison A. Bailes III, GreenBuildingAdvisor report
The Causes Cannot Be Quantified
The report does not establish the exact portion of the increase caused by the stepson’s baths, the dirty filter, or the dirty coil. It also does not provide monthly hot-water volumes, controlled tests, or data from another comparable unit. The timing of the drop after the coil cleaning could be relevant, but it does not by itself prove that cleaning caused the full decline, particularly because the additional household member moved out around the same period.
The 2026 annual figure is partly estimated, and the article’s findings concern one home. It does not establish how much energy another household should expect to save from cleaning, filtration changes, or adjustments in water use.
Track Use and Check the Unit
Bailes recommends covering or turning off a heat-pump water heater during dusty work, checking and cleaning its filter regularly, and cleaning the coil and other components when they become dirty. He also suggests considering improved filtration and monitoring energy consumption so changes can be compared with maintenance, occupancy, and seasonal conditions. Owners should follow the manufacturer’s maintenance instructions and seek qualified service if they are unsure how to clean components safely.
For a household seeing a rise, the report’s approach is to compare monthly readings—not just annual bills—with changes in hot-water use and the unit’s condition. Further tracking may show whether consumption returns to its previous pattern, but the report provides no additional measurements that would settle the precise contribution of each factor.
Key Questions
What caused the reported water heater energy increase?
In this home, higher hot-water demand and dust on the filter and coil both likely contributed. The report says the available data cannot determine each factor’s exact share.
How much did energy use rise?
The water heater’s annual energy use in 2024 was 89% higher than in 2020, according to the report. That comparison applies to the author’s unit and does not predict another household’s consumption.
Can a dirty filter make a heat-pump water heater use more energy?
The report says dust can dirty the filter and coil, and that these conditions likely affected the unit’s efficiency. It does not quantify the energy penalty or establish a general figure for other models.
What should I check if my water heater’s energy use rises?
Compare monthly energy readings with changes in household hot-water use, then inspect the filter and follow the manufacturer’s maintenance guidance. Consider whether renovation dust or other airborne debris could have reached the unit.
Did cleaning the coil return the unit to normal?
Consumption fell sharply after the coil was cleaned, but the report does not attribute the full decline to cleaning. The additional household member also moved out around that time, making the causes difficult to separate.
Source: greenbuildingadvisor.com
