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A GreenBuildingAdvisor report traced a homeowner’s unusually high heat-pump water heater energy use in 2024 and 2025 to more than one likely factor. A family member’s bath use increased hot-water demand, while renovation dust may have reduced the heater’s efficiency; the available data could not separate their effects.
A homeowner’s heat-pump water heater used unusually more energy in 2024 and 2025, but the spike was not explained by renovation dust alone, according to a GreenBuildingAdvisor report by building-science consultant Allison A. Bailes III. The increase began after a stepson who preferred baths moved into the home in August 2023, while a dusty filter and coil during a basement renovation may also have made the system less efficient.
Bailes tracked the heater’s electricity use alongside household energy bills. In 2024, the water heater’s annual use was 89% higher than in 2020, and 2025 was also unusually high. The report does not provide a separate measurement of hot-water volume, so the electricity figures alone cannot show how much of the increase came from heavier use versus reduced equipment efficiency.
The basement renovation began in February 2024 and generated dust and other airborne particles. Bailes said he did not always cover or turn off the heater during the work. A heat-pump water heater draws heat from indoor air, and the report describes a heavily soiled filter as well as dirt on the coil and other components. Bailes said these conditions likely affected energy use.
Monthly data complicated that explanation: consumption began rising sharply at the end of 2023, before the renovation started. The stepson had moved in several months earlier and stayed for two years, leaving at the end of July 2025. The heater’s use then fell sharply in July 2025, after the move-out and after Bailes cleaned the coil in April. The timing supports a role for both household demand and maintenance, but does not isolate either one.
Why the Spike Had Two Likely Causes
The report shows why a higher utility reading does not automatically mean an appliance has failed. In this case, the same energy trend could reflect both more hot water being used and less efficient heat transfer from dirt on the filter and coil. Without monthly hot-water-use data, the homeowner could not calculate each factor’s contribution.
That distinction matters for people trying to reduce bills. Cleaning or maintaining equipment may help, but it will not remove extra demand caused by a change in household routines. Conversely, a change in occupancy does not rule out a maintenance issue. Bailes recommends monitoring energy use, checking and cleaning the filter, and cleaning the coil and other components when dirty. He also advises covering and turning off the unit during dust-producing work and upgrading filtration.
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Renovation and Household Changes
The report compares use from 2020 onward, when Bailes says the monthly pattern was relatively regular: about 60 kilowatt-hours per month in winter and roughly 20 to 30 kWh per month in summer. A gradual increase preceded the more pronounced rise, which became apparent near the end of 2023.
The renovation had mixed effects. It dirtied the equipment, but it also placed the water heater in fully conditioned basement space. Before the winter of 2024–25, the basement was not heated. Bailes said the warmer surrounding air would have improved the heat pump’s operating conditions and kept winter energy peaks from being higher. The report’s 2026 annual figure includes an estimate for the final four months of that year, rather than a complete year of observed data.
“the jolt in energy use those two years actually was caused by both things”
— Allison A. Bailes III, in GreenBuildingAdvisor
How Much Each Factor Added
The report does not quantify how much additional electricity was attributable to the stepson’s baths, the clogged filter, or dirt on the coil. It also does not include monthly hot-water volume or a controlled comparison with the same household demand before and after cleaning. The coinciding drop in July 2025 followed both the stepson’s departure and the April coil cleaning, so the available timeline cannot establish a single cause. The claimed effect of the warmer basement is also not quantified.
Monitoring Use and Equipment
Bailes says homeowners with heat-pump water heaters can track energy consumption, inspect the filter regularly, and clean it when needed. During remodeling or other dusty work, he recommends turning off and covering the unit; the coil and other parts should be cleaned when they become dirty. The report does not identify a further test or measurement that would determine the separate contribution of demand and equipment condition in this household. For readers seeing a similar rise, tracking occupancy, hot-water habits, maintenance and energy use together may help identify what changed.
Key Questions
What caused the water heater’s energy use to rise?
The report points to two likely contributors: increased hot-water demand after a stepson moved in, and reduced efficiency from dust and dirt on the heat-pump water heater’s filter and coil during a basement renovation. Their individual effects were not measured.
Did renovation dust explain the whole increase?
No. Monthly energy use began rising at the end of 2023, before the renovation started in February 2024. The timing of the increase also matched a change in household occupancy.
How much more energy did the heater use in 2024?
According to Bailes’s report, the heater used 89% more energy in 2024 than in 2020. That comparison is annual energy use for those two years; the report does not give a separate figure for the share caused by dirt or additional hot-water use.
What maintenance does the report recommend?
Check and clean the filter as needed, clean the coil and other components when dirty, and cover and turn off the heater during dust-producing work. Bailes also recommends monitoring energy use and says homeowners can upgrade filtration.
Source: greenbuildingadvisor.com
