A dirty mini-split does the same job with more electricity. The U.S. Department of Energy states that dirty filters, coils, and fans reduce airflow, that reduced airflow decreases performance and can damage the compressor, and that the energy-use difference between a well-maintained heat pump and a severely neglected one can range from 10% to 25%. New Hampshire's average residential electric price was 27.01 cents per kilowatt-hour in June 2026, the highest tier in the country. For a Lakes Region home whose mini-splits use 5,000 to 7,500 kWh a year, that penalty works out to roughly $135 to $500 a year.
The physicsWhy does a dirty coil use more electricity?
Because a mini-split moves heat by pushing air across a coil, and dirt gets in the way of both halves. A film of dust and biofilm on the evaporator fins insulates the aluminum, so less heat moves per minute of run time. A loaded blower wheel pushes less air across those fins, so even less heat moves. The unit responds by running longer and harder to hit the same setpoint, and every extra minute is metered.
The ENERGY STAR maintenance checklist puts it plainly: dirty coils reduce the system's ability to cool your home and cause the system to run longer, increasing energy costs and reducing the life of the equipment. DOE's Energy Saver 101 home cooling guide adds that routinely replacing or cleaning air filters alone can lower an air conditioner's energy consumption by 5 to 15 percent, and DOE's Energy Saver guide says following a regular maintenance schedule can reduce heating and cooling costs by 10% or more.
What is the electric rate in New Hampshire right now?
The U.S. Energy Information Administration reported New Hampshire's average residential price at 27.01 cents per kilowatt-hour for June 2026, versus a national average of 18.34 cents. That is the all-in figure, supply plus delivery, and it is the number to use for a rough annual estimate.
The pieces behind it: Eversource, which serves Laconia, Tilton, Franklin, and much of the western Lakes Region, set its residential Rate R default supply at 14.009 cents per kWh for August 1, 2026 through January 31, 2027, with delivery charges on top. NH Electric Co-op, which serves Meredith, Moultonborough, Wolfeboro, Alton, Plymouth, and Bristol, moved its Co-op Power Charge to 13.9 cents per kWh on August 1, 2026, alongside a 4.0-cent Regional Access Charge and a 5.9-cent Distribution kWh Charge, before fixed monthly charges. Either way, a kilowatt-hour in the Lakes Region costs in the mid-twenties of cents.
Worked exampleHow much can a dirty coil cost a Lakes Region home per year?
Take a year-round home in Gilford with two mini-splits that carry most of the heating and all of the cooling, using about 5,000 kWh a year for the mini-split, and a larger three-mini-split home in Meredith at about 7,500 kWh. Those usage figures are assumptions for the example; your own number is on your utility's usage history, and a heat-pump-only home in a cold Lakes Region winter can run higher. Apply the DOE range at 27.01 cents.
| Scenario | Annual mini-split use | Annual cost, clean | 10% penalty | 25% penalty |
|---|---|---|---|---|
| Two mini-splits, year-round home | 5,000 kWh | $1,351 | $135 | $338 |
| Three mini-splits, year-round home | 7,500 kWh | $2,026 | $203 | $506 |
| One mini-split, bedroom, summer plus shoulder seasons | 1,500 kWh | $405 | $41 | $101 |
| Seasonal camp, two mini-splits, May–October | 2,500 kWh | $675 | $68 | $169 |
Now put the cleaning cost beside it. A deep clean of two mini-splits on one compressor is $318, and three mini-splits on one compressor is $437. At the neglected end of DOE's range the annual penalty still covers the job in year one, though the two-mini-split case is close: $338 against $318, and $506 against $437 for the three-mini-split home. At the 10% end it is not close at all — $135 against $318, and $203 against $437, or a little over 40% of the job, which means roughly two and a half years to pay back on electricity alone. So the honest version is this: if your units are genuinely neglected, the power bill covers the clean in the first year. If they are in decent shape, it does not, and the electricity is one reason among several rather than the whole case. The others are the reasons most people actually call: the smell, the drip, the weak bedroom on a hot night, and the compressor DOE warns can be damaged by restricted airflow.
Which parts matter most?
Coarse dust on the mesh restricts airflow before it reaches anything else. This is the 5 to 15 percent DOE attributes to filter care, and it is the homeowner's job every two to four weeks.
A felted wheel is the biggest airflow loss inside the unit. Airflow drives everything downstream, so a dirty wheel drags the whole system.
Fouled fins transfer less heat and, in cooling, hold water longer. In heating they force longer defrost-and-recover cycles at the outdoor unit.
A condenser plastered with pine needles and cottonwood fluff rejects heat poorly in summer and absorbs it poorly in winter. A low-pressure rinse each spring is enough.
A plugged drain does not use electricity directly, but a coil sitting in a full pan stays wet and fouls faster.
Growth on the outlet is cosmetic for efficiency but a tell for everything above.
Does cleaning the coil pay for itself?
On a multi-unit system that heats and cools most of the year, the DOE range at New Hampshire rates puts the annual electricity penalty between roughly 40% of and slightly more than the cost of cleaning every unit: $135 to $338 against a $318 two-mini-split clean, $203 to $506 against a $437 three-mini-split clean. At the neglected end it pays for itself in the first year; at the maintained end it takes a bit over two. The payback lands nearer the first year the harder the system runs between cleanings. A lightly used single mini-split in a spare room takes longer to pay back on electricity alone and is usually cleaned for the odor and the air rather than the bill. Wood-heat homes and camps closed up damp sit at the neglected end of the range and pay back fastest.
FAQEnergy cost questions
How much more electricity does a dirty mini-split use?
DOE puts the gap between a well-maintained and a severely neglected heat pump at 10% to 25%, and says clean filters alone can cut AC energy use 5 to 15 percent.
What is the electric rate in New Hampshire in 2026?
EIA reported 27.01 cents per kWh average residential for June 2026. Eversource's default supply alone is 14.009 cents from August 2026 through January 2027, before delivery.
What does that cost a Lakes Region home per year?
About $135 to $338 a year at 5,000 kWh, and $203 to $506 at 7,500 kWh, using DOE's range and the EIA rate.
Does cleaning pay for itself?
It depends on the shape the units are in. On a hard-running, genuinely neglected system the electricity penalty covers the job in year one: $338 a year against a $318 two-mini-split clean. On a system in decent shape it is closer to $135 a year against that $318, so a bit over two years on electricity alone. Odor, comfort, and compressor life are the rest of the case.
Related guides: what cleaning costs in NH, how often to clean, and why wood heat pushes units to the neglected end. The seasonal maintenance service keeps a cleaned system at the maintained end.