Heat pump filters and maintenance

The basic schedule from ENERGY STAR, DOE and NRCan: check the filter monthly, change or clean it at least every three months, and have a technician service the system once a year.^{[Source 1][Source 3][Source 4]} Ductless units have washable filters in each indoor unit that usually need cleaning more often.

Filters in ducted systems

ENERGY STAR: "Check your filter every month... If the filter looks dirty after a month, change it. At a minimum, change the filter every 3 months."^{[Source 1]} DOE says to "clean or change filters every 3 months or as recommended by the manufacturer."^{[Source 3]} NRCan explains why: "clogged filters will decrease airflow and reduce the efficiency of your system."^{[Source 4]}

The monthly check tells you whether yours needs changing sooner than three months.

Which filter rating

Filters are rated by MERV (Minimum Efficiency Reporting Value); higher MERV captures smaller particles. EPA recommends choosing "a filter with at least a MERV 13 rating, or as high a rating as your system fan and filter slot can accommodate."^{[Source 5]}

EPA's air cleaner guide adds: "Most furnaces and HVAC systems can accommodate a MERV 13 filter without creating equipment problems, provided that the filter is replaced frequently."^{[Source 10]} If you are moving to a higher MERV filter and are unsure about your system, a technician can measure the system's Static pressure with the new filter in place.

Filters in ductless units

Wall and ceiling units have their own filters behind the front panel. Mitsubishi's operation manual for one wall unit series states: "It is therefore recommended to clean air filters every 2 weeks." The manual says to remove dirt with a vacuum or rinse with water, and not to use water hotter than 50°C (122°F).^{[Source 6]} Check the manual for your model; schedules differ.

Outdoor unit

• Keep it clear. Carrier's 25VNA owner's manual calls for "a 12" (305 mm) minimum clearance" from grass and shrubs.^{[Source 7]} The installation manual for your model sets its own clearances.
• Snow. Lennox's guide says to "keep the snow level below the louvered panels."^{[Source 8]} See Ice on the outdoor unit.
• Debris. Keep leaves and debris off and around the unit. For any cleaning of the coil itself, follow your owner's manual.

Indoor vents

NRCan: "be sure that vents and air registers in your home are not blocked by furniture or carpeting, as inadequate airflow to or from your unit can shorten equipment lifespans and reduce efficiency of the system."^{[Source 4]}

Professional maintenance

• How often. DOE: "have a professional technician service your heat pump at least once a year."^{[Source 3]} NRCan says the same.^{[Source 4]} ENERGY STAR's checklist suggests checking "the cooling system in the spring and the heating system in the fall."^{[Source 2]} Lennox's guide recommends inspection before both the cooling and heating seasons.^{[Source 8]} DOE and NRCan give once a year as the minimum.
• Why. DOE says the difference in energy use between a well-maintained heat pump and a severely neglected one ranges from "10% to 25%."^{[Source 3]}
• Refrigerant. Any work involving refrigerant must be done by a technician certified under EPA Section 608.^{[Source 9]}

A simple calendar

When	Task
Monthly	Check the filter; change if dirty
Every 2 weeks to monthly (ductless)	Clean indoor unit filters per the manual
Every 3 months at most	Change or clean the filter even if it looks fine
After storms and snow	Clear snow, ice and debris from around the outdoor unit
Once or twice a year	Professional service