Is your heat pump too loud? Sources and quiet fixes

What is a normal heat pump noise level?

Manufacturers publish a sound rating for the outdoor unit in decibels, usually weighted as dBA. Lower is quieter, and every extra ten decibels is heard as roughly twice as loud. Ratings are measured close to the unit under test conditions, so the level at your bedroom window will be lower than the number on the spec sheet, and distance and surfaces change it again.

What you hear on a normal day is a low fan sound with a faint compressor note underneath. Variable-speed models ramp up and down gradually, which is easier on the ear than the old on-off cycling. The sound is loudest on the coldest days, when the unit works hardest, and during the defrost cycle, which is covered in the guide to heat pump defrost and noise.

Where does the sound come from?

Four sources account for most complaints.

• The outdoor fan. Air moving through the coil makes a whoosh that rises with fan speed.
• The compressor. It adds a low hum, and a lower tone can travel through the ground and the wall of the house.
• Vibration. A unit that sits on an uneven pad or touches the wall can turn a small hum into a drone inside the room.
• Indoor equipment. The air handler blower and the ducts make airflow noise that is easy to mistake for the outdoor unit. Duct size matters here, as the guide to heat pump load calculation explains for sizing.

Rattling panels, a loose fan guard or a buzzing contactor are repair items. A bent fan blade or a failing compressor bearing is a louder, rougher sound that gets worse over weeks.

How can you reduce heat pump noise?

Start with the cheap checks. Make sure the unit is level on a firm pad, that nothing touches it, and that the refrigerant lines are not rubbing on the wall. Vibration pads and flexible line sets are standard fixes for a drone that carries into the house. Tightening loose panels and clearing leaves from the fan guard costs little.

Next, look at location. A unit tucked into a corner or placed under a bedroom window bounces sound back at the house. Moving it, or giving it more open space, often does more than any accessory. Our guide to heat pump sizing for cold climates also matters, because an oversized unit cycles more, and a correctly sized variable-speed unit mostly runs at a low, steady speed.

Sound blankets for the compressor and a solid fence or screen can help when the site is tight. Leave clearance around the coil, since a barrier that blocks airflow hurts performance and can cause icing. Many models also have a quiet or night mode that caps fan speed at a small cost in output, which a technician can enable.

Do noise rules apply to heat pumps?

Many municipalities set limits on the sound a mechanical unit may make at the property line, and some set minimum distances from a neighbour's lot. The rules differ from one town to the next, so check the noise bylaw and the zoning or permit requirements with your municipality before choosing a location. Condominium and strata corporations may add their own placement rules.

Placement is as much a neighbour question as a bylaw question. A unit facing a shared fence or a neighbour's bedroom window causes friction even when it meets the limit. The guide to outdoor unit placement covers clearances, snow and sightlines in more detail.

When is the noise a sign of a problem?

Call a qualified technician for banging, screeching, grinding, a loud buzz that did not exist before, or a sound that changes with each cycle. Ice build-up with a noisy fan can point to a defrost fault. These problems usually grow, and running a damaged compressor can turn a small repair into a replacement. Regular servicing catches loose parts early, and the heat pump maintenance checklist lists what to check each season.

Ground-source systems have no outdoor fan, so their noise is mostly indoors, from the compressor cabinet. That is one reason people compare them in the air-source versus ground-source guide.

Quick answers