How Noisy is a Heat Pump?

Heat pumps for heating and cooling a home are growing in popularity due to their efficiency, dropping costs, and federal incentives.

When I installed a heat pump at my home, it replaced an old central air conditioner with an outdoor unit that was so noisy that it was difficult to have a conversation on my patio. When I upgraded that old unit for a heat pump, the loud rattling of that 20+ year old A/C was replaced with a moderate hum of the new unit. While it isn’t silent, the noise of the heat pump is much less annoying when we’re having guests on patio.

I used a sound level measuring app on my phone, and it told me that the sound level at about 4 feet away from my heat pump’s outdoor unit was about 60 decibels. According to several expert sources, that’s about as loud as a normal conversation. I’d say that’s accurate. It’s loud enough to be noticeable, but much less annoying than my old air conditioner, which was louder than my vacuum cleaner.

My neighbors installed a mini-split heat pump system with slim profile outdoor units, and it is much quieter than mine - maybe 50 dB or lower. In fact, standing next to it, you might not even notice that it’s on.

That’s my observation about the outdoor noise of a heat pump during normal operation, but there are different sounds you can expect to hear from your heat pump system. If you’re concerned having a heating and cooling system for your home that’s quiet, keep reading to learn about the sound levels you can expect from a heat pump.

How noisy is the outdoor unit for a heat pump?

Residential heat pumps are almost always split systems, which means that the system is divided into indoor and outdoor components.

The outdoor unit, sometimes referred to as the condenser coil, is typically a large square-ish unit in the case of a central ducted heat pump, or a slimmer rectangular unit if the system is a ductless mini-split.

You can discuss with your HVAC installer where you can place the outdoor unit, but the best placement is dictated by a few considerations, including having an area free of obstructions for good airflow. A shady area is also preferred to improve its cooling performance in the summer. If you’re lucky, that will mean that it can be tucked away from any outdoor patios or open windows, in which case noise is less of a concern.

However, sometimes the installation options are limited, and you’ll be forced to place the unit near an outdoor seating area or a window that you often have open. In this case, the noise level of the outdoor unit will be more of a concern.

Fortunately, modern heat pumps have features such as sound insulation, anti-vibration mountings and specially shaped fan blades that help to reduce the noise they make.

That said, some heat pumps are quieter than others, and the noisiest models might be noticeably loud if they’re placed directly beside an outdoor seating area. I looked up the technical specifications of a few of the most popular heat pump brands, and came up with the table below of the range of minimum and maximum sound levels for the outdoor units in their product lineups:

As you can see, there can be a big difference in noise levels between heat pump models. Notably, Mitsubishi’s product lineup is quieter than others because all of their models are slim profile units.

A quick side note about decibels

For those of you who aren’t familiar with decibels (dB), which are used to measure sound levels, here’s a quick explanation. Decibels use a logarithmic scale in which an increase of 10 dB refers to sound that is 10 times louder. Here’s a table describing what different decibel levels mean in the real world:

(Source: OSHA)

Thankfully, none of the heat pumps are as loud as a freight train, but there’s a big difference between a heat pump that is quieter than the typical house and one that is louder than a classroom.

Slim profile outdoor units are usually quieter than conventional “box” designs

As mentioned earlier, slim profile are usually the quietest type of heat pump. These have fans that blow air out the side, so they are sometimes referred to as side discharge units. They are most commonly paired with ductless mini-splits, but some can be used with central ducted setups too, such as the Trane XV19 unit pictured below.

Looking at the specifications published by Trane, the XV19 has a noise level range of 43-57 dB. For comparison, the Trane XV18 with a more conventional “box” design has a noise rating of 55-76 dB - nearly 100 times louder.

Keep in mind that if one heat pump is about as noisy as a whisper, a model that is 100 times louder still isn’t that noisy. However, it will be audible, and potentially loud enough to be annoying.

Two-speed and multi-stage heat pump are usually quieter

There are many times when your home doesn’t need your HVAC system to be running at full power. This is when two-speed and multi-stage heat pumps have an advantage. When your home needs only a moderate amount of heating or cooling, these heat pumps can operate at a lower power level. This not only gives you energy savings, but the fan and compressor in the outdoor unit will be running at a lower speed, resulting in less noise.

In contrast, single speed heat pumps always work at full power. This means that they’ll tend to be more noticeable when operating.

Forced air system will always generate some white noise

If you have a central ducted heat pump – that is, a forced air system with air registers – you’ll have some noise from the air ducts. This is the same noise that you’ll experience with any forced air system, which is caused by high pressure air moving through the metal ducts. A heat pump has an indoor heat exchanger, but it doesn’t have any components that generate noise.

One thing I’ve noticed with my central ducted heat pump, which uses a gas furnace as backup heat on the coldest winter days, is that the system is actually a little bit quieter when operating the heat pump than it is when the furnace is on. This is because I can actually hear the roar of the flames from the combustion chamber in the furnace. It isn’t actually that loud, but it means that the white noise sound of the furnace is a little louder than just the sound I hear from the blower motor when the heat pump is running.

These sounds will vary depending on the installation, so you might not hear anything at all from your furnace. Or yours might be louder than mine, depending on its size, location of the furnace, and configuration of your ducts.

Variable speed heat pumps will also be quieter indoors

If you have a central ducted system, a multi-speed heat pump will be quieter both indoors and outdoors when it’s operating in a reduced power mode.

This is because the blower motor that pushes air through the ducts will run at a lower speed when the heat pump isn’t at full power. This reduces the air pressure in the ducts, which also reduces that sound that you’ll hear. Some multi-stage heat pumps can reduce their power output to as low as 25%. At that power output, the system will basically be silent.

Ductless head units are very quiet

From what I’ve observed, ductless mini-splits, which use an indoor head unit that has an internal fan, are basically silent. They have adjustable fan speeds, so on the highest settings you may sometimes hear a faint sound, but from I’ve experienced, these systems are much quieter than the forced air ducts in my home.

Unusual sounds you might hear from the outdoor unit

In the winter, one common sound that you might hear is the defrost cycle. The defrost cycle sends heated refrigerant to the outdoor unit for several minutes to eliminate any ice build up.

With my heat pump, I hear a loud buzzing sound when defrost mode is active. In other heat pumps, the sound might be different: it’s sometimes described as a loud whooshing sound.

While this can be loud, the bottom line is that this is part of its normal operation, and you shouldn’t be alarmed by it.

Other sounds, however, may not be normal. Squealing sounds may indicate a worn belt or bearings, while vibration sounds can be caused by loose or damaged parts. If you notice that the fan in your outdoor unit is louder than it has been in the past, that might indicate worn bearings. Unusual sounds like this warrant a call to your HVAC company.

Bottom line: heat pumps models vary from “pretty quiet” to “basically silent”

In general, heat pumps operate pretty quietly, but some models may be loud enough to be a little annoying if they are located near outdoor spaces. In addition, ducted (forced air) systems always generate some noise, whether the heating system is a furnace or heat pump.

For some, this might not matter at all. For me personally, the noise can be a little intrusive. For example, when watching TV at night with the volume low, the white noise from my air ducts requires me to raise the TV volume a little.

If this sort of thing is of a concern to you, there are a few options to make sure that your heat pump system is the quietest possible:

• Opt for a slim profile outdoor unit. While these are typically used with ductless mini-split systems, some manufacturers make them compatible with central ducted systems too.
• Two-speed and multi-stage heat pumps operate more quietly because they are able to run for longer periods at low power.
• Mini-split systems have very quiet indoor units that don’t generate the kind of white noise that forced air ducts do.