ManualHarbor

Heat Pump Maintenance Checklist

Updated October 9, 2026

A heat pump needs routine care from you and from a technician. Check the filter and the outdoor unit once a month, keep the outdoor unit clear of plants, debris and snow, and schedule professional service at least once a year, as the U.S. Department of Energy recommends. Lennox and Carrier go further and recommend two visits a year, one before cooling season and one before heating season. Upkeep affects your bills: DOE says a severely neglected heat pump can use 10% to 25% more energy than a well-maintained one.

The checklist at a glance

  • Monthly — Task: Check the indoor filter; clean or replace it if dirty; Who: Homeowner; Source: ENERGY STAR, Lennox
  • Monthly — Task: Clear leaves, grass clippings and paper from the outdoor unit; Who: Homeowner; Source: Lennox
  • Monthly — Task: Check the condensate drain line for blockages (ask your dealer to show you how first); Who: Homeowner; Source: Lennox
  • Every 2 weeks (peak season) to monthly (light use) — Task: Clean ductless indoor-head filters, or follow your manual's interval; Who: Homeowner; Source: Trane/Mitsubishi
  • At least every 3 months — Task: Change or clean the ducted filter, unless the manufacturer specifies otherwise; Who: Homeowner; Source: DOE, ENERGY STAR
  • Spring and summer — Task: Keep plants 2 feet back on all sides and 4 feet of open space above; Who: Homeowner; Source: Trane
  • Whenever dirty — Task: With power off, gently hose off the outdoor coil; never use a pressure washer; Who: Homeowner; Source: DOE, Trane, Lennox
  • As needed — Task: Clean supply and return registers and straighten bent register fins; Who: Homeowner; Source: DOE
  • Fall and winter — Task: Keep snow below the unit's louvered panels and clear heavy snow off the top; Who: Homeowner; Source: Lennox, Trane
  • Before each season (at least yearly) — Task: Professional inspection and tune-up; Who: Licensed technician; Source: DOE, Lennox, Carrier

If you aren't sure where your filter is or how to check the drain, ask your installer to walk you through it once. Lennox's homeowner guide recommends this. Shut off power at the disconnect switch before any hands-on maintenance, and follow your own owner's manual where it differs from this list.

What the professional visit should cover

DOE's technician checklist for heat pumps covers:

  • Inspect ducts, filters, blower and indoor coil for dirt and obstructions.
  • Find and seal duct leaks.
  • Measure airflow and refrigerant charge (not just estimate them) and check for leaks.
  • Clean and tighten electrical connections.
  • Lubricate motors and inspect belts.
  • Confirm heating is locked out when the thermostat calls for cooling, and the reverse.
  • Check that the thermostat works correctly.

Carrier's heat pump checklist adds checks specific to heat pumps: testing the defrost cycle, checking the reversing valve and testing the auxiliary heat. It also includes inspecting the run capacitor.

Two items deserve attention. First, airflow: DOE recommends about 400 cubic feet per minute (cfm) per ton of cooling capacity, and says performance drops if airflow falls well below 350 cfm per ton. Second, refrigerant charge: DOE notes that split systems are charged on site, so they can end up overcharged or undercharged, and both conditions reduce efficiency. DOE also says the system should be leak-checked on every service call.

Ask the technician about auxiliary heat controls too. DOE calls unnecessary heat-strip operation one of the most commonly violated installation practices. In DOE's example, a 50°F day with a thermostat raised from 66°F to 70°F should never turn on the strip heat.

Defrost: what's normal and what isn't

In heating mode, the outdoor coil pulls heat out of cold outdoor air, and frost can build up on it. Lennox's homeowner guide says frost forms on the coil when it's below 45°F outside. To clear it, the system briefly reverses refrigerant flow to warm the coil. DOE describes this as the job of the reversing valve.

Normal behavior (per Lennox and Carrier):

  • Defrost cycles last about 5 to 15 minutes and repeat at preset intervals. Lennox says a heat pump should defrost itself automatically every 30 to 90 minutes in cold, humid weather.
  • Steam rising from the outdoor unit during defrost.
  • Backup (auxiliary) heat turning on briefly to keep the house warm, or a short period of cooler air from the vents.
  • A thin layer of frost on the coil. Carrier treats frost under 1/4 inch as normal if it clears during defrost.

Call a technician if:

  • Ice is thicker than 1/4 inch, coats the coil solidly or doesn't clear after a defrost cycle. Carrier says to turn the system off in that case.
  • The unit refreezes quickly after thawing, ice forms on the refrigerant lines, the fan doesn't spin after the ice melts, or the unit runs for hours without defrosting (Lennox).

If you're shopping for a new unit, DOE recommends choosing one with demand-defrost control, which keeps the number of defrost cycles to a minimum. You can browse ENERGY STAR certified models on our heat pump pages.

Keeping the outdoor unit clear of snow and ice

  • Don't wrap it. DOE warns against covering a heat pump's outdoor unit in winter because a cover keeps it from heating properly. Lennox says a cover over the top only (a snow guard) is acceptable, but the sides must stay open.
  • Watch the snow line. Lennox's homeowner guide says to keep snow below the louvered side panels. Trane recommends clearing heavy snow off the top and away from the sides.
  • Use a soft broom, not tools. Lennox recommends gently sweeping light snow off the top and not piling shoveled snow against the unit.
  • Never chip ice or pour hot water on the coil. Lennox warns that hot water can crack components and that chipping can damage the coils, fins and fan blades.
  • Check roof runoff. Make sure gutters and downspouts don't drain onto the unit, where the water can refreeze (Lennox).
  • Placement matters. DOE notes that outdoor units may need to be raised above expected snow levels and shielded from strong winds, which can interfere with defrost. Raising or moving the unit is a job for the installer.
  • After a long power outage. Lennox's guide for its heat pumps says to use the thermostat's EMERGENCY HEAT setting if the power has been out for several hours or more. Allow six hours for the compressor's crankcase heater to warm up before switching back to normal HEAT. Check your own manual, because procedures differ by brand.

Ductless mini-split heads: filter cleaning

Each indoor head of a ductless mini-split or multi-split system has its own washable filter. Lennox points out that this makes ductless upkeep more involved when one outdoor unit serves several rooms.

Filter cleaning intervals depend on the model. Trane's guidance for its Mitsubishi-built ductless units is to clean as often as every two weeks in peak heating or cooling season and about once a month when use is light. One older Fujitsu wall-unit manual calls for cleaning every five weeks under normal use. Your owner's manual sets the right schedule for your system.

A typical cleaning routine, based on Trane/Mitsubishi and Fujitsu instructions:

  1. Turn the head off with the remote or wall control. Fujitsu also tells owners to switch off the breaker before cleaning.
  2. Lift the front panel and slide the filters out gently so dust doesn't shake loose.
  3. Vacuum with a brush attachment on low suction, or rinse with lukewarm water. Fujitsu allows a mild detergent. Some Mitsubishi units have small deodorizing filters that must stay dry.
  4. Let the filters dry completely, out of direct sun, before putting them back.
  5. Don't touch the coil fins behind the filters, and don't run the unit without filters installed (Fujitsu).

Trane says its Mitsubishi ductless filters can last up to 10 years if handled carefully. For professional service, Trane recommends a visit at least once a year, preferably twice, and Lennox recommends twice a year. Lennox's mini-split checklist includes electrical connections, capacitors, refrigerant connections and condensate drain hoses.

Geothermal heat pumps

Geothermal heat pumps exchange heat with the ground instead of the outdoor air. DOE says they need little maintenance and estimates the indoor components last up to 24 years and the ground loop 50 years or more. The defrost and snow items above apply to air-source units. For a geothermal system, follow your installer's schedule for filter changes and professional checks.

What not to do

  • Don't add refrigerant or open refrigerant lines. Under EPA Section 608 rules, only certified technicians may service equipment that could release refrigerant, and intentionally venting refrigerant is prohibited.
  • Don't open electrical panels. Carrier warns that capacitors can store a lethal charge even after the power is off.
  • Don't pressure-wash the coil. Trane warns against pressure washers, and Lennox says high-pressure water can damage the coil's metal fins.
  • Don't run the system with the filter or access panels removed (Lennox).
  • Don't set the thermostat back so far that backup heat kicks in. DOE notes electric resistance backup heat usually costs more to run.
  • Don't aim sprinklers at the unit. Lennox says long exposure to treated water corrodes steel and aluminum parts.

FAQ

How often should a heat pump be professionally serviced?

DOE says at least once a year. Lennox and Carrier recommend twice a year, before the cooling and heating seasons. Because a heat pump runs in both seasons, a fall visit lets the technician test defrost and backup heat before cold weather.

Why is my heat pump steaming and blowing cooler air in winter?

It's most likely in a defrost cycle. Lennox describes steam during defrost as normal, and Carrier says a brief period of cooler air can be normal too. If thick ice remains after the cycle ends, turn the system off and call a technician.

Should I cover my heat pump for winter?

No. DOE warns that covering the outdoor unit keeps it from heating properly. Lennox suggests at most a top-only snow guard that leaves the sides open.

How often should I clean mini-split filters?

Follow your manual. Trane/Mitsubishi guidance ranges from every two weeks in peak season to monthly in light use, while one Fujitsu manual specifies every five weeks.

Can I recharge a heat pump's refrigerant myself?

No. Refrigerant work requires EPA Section 608 certification. DOE also says the correct charge should be confirmed with measurements, which requires a technician's tools.

Related guides

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