Heat Pumps Explained for Homeowners

Here is the idea that makes heat pumps click for most people: a heat pump doesn't make heat, it moves it. Your refrigerator already does this every day. It pulls heat out of the food compartment and releases it through coils into your kitchen, which is why the area around it feels warm. A heat pump does the same job at the scale of a house, and it can run the process in either direction.

In summer it pulls heat out of your rooms and dumps it outside, just like a central air conditioner. In winter it reverses, gathering heat from the outdoor air (or the ground) and bringing it inside. Once that clicks, most of the quirks homeowners notice start to make sense.

Moving heat instead of making it

A typical air-source heat pump has two main parts: an outdoor unit with a compressor, a fan and a large coil, and an indoor unit, usually an air handler, with another coil and a blower. Refrigerant travels between them through copper lines. When refrigerant evaporates it absorbs heat, and when it is compressed and condenses it releases heat. The compressor keeps that cycle going.

A part called the reversing valve decides which way the heat flows. In cooling mode, the indoor coil absorbs heat and the outdoor coil gets rid of it. In heating mode, the roles swap. Air that feels cold to you still holds some heat, and the system is designed to collect it. Because the equipment is moving heat rather than burning fuel, there is no flame or combustion in the heat pump itself.

The types you will run into

Heat pumps come in a few common forms, and your options depend on the house you have.

Ducted air-source systems

These look a lot like a central air system, with an outdoor unit and ductwork to each room. They are a common replacement for an aging air conditioner in homes that already have ducts.

Ductless mini-splits

These use one outdoor unit connected to one or more wall, ceiling or floor units inside. They suit additions, older homes without ducts, finished attics and rooms that never feel comfortable.

Ground-source systems

Often called geothermal, these move heat through buried loops of piping instead of the outdoor air. Installation involves excavation or drilling, and local permit rules for that work vary.

Dual-fuel setups

These pair a heat pump with a gas or oil furnace that takes over in the coldest weather. The system switches between them based on settings your installer chooses. You may also see packaged units, where every component sits in one cabinet outdoors, in some regions.

What happens when it gets cold

As the outdoor temperature drops, there is less heat in the air to collect, and a heat pump works harder to deliver the same comfort. Newer cold-climate models are built to keep working in much colder weather than older units, but every system has limits, and your installer should explain how yours was sized for local winters.

Most systems have backup heat, often electric heat strips in the air handler or a furnace in a dual-fuel setup. When the thermostat shows AUX, the backup is helping out. The emergency heat setting is different: it shuts off the heat pump and runs only the backup, and it is meant for times when the heat pump has a problem. Leaving it on as a normal setting can run up your energy use.

You may also notice the outdoor unit going quiet, then making a whoosh, with steam rising off the coil. That is a defrost cycle. In cold, damp weather, frost builds up on the outdoor coil, and the system briefly reverses to melt it. It is normal and usually lasts a few minutes. Heavy ice that never clears, or a unit encased in ice, is a reason to call a technician.

Thermostat habits that suit a heat pump

Heat pumps tend to prefer steady settings. A deep overnight setback can force the system to lean on backup heat in the morning to catch up, which is exactly what you were trying to avoid. Many homeowners find a small setback, or none at all, works well. Ask your installer what they recommend for your equipment.

Air from the vents may also feel warm rather than hot. A heat pump often delivers air at a lower temperature than a furnace, over longer run times. That is how it is designed to work, so a system that runs longer doesn't necessarily mean something is wrong. Make sure your thermostat is designed for heat pumps, since a mismatched thermostat can manage backup heat poorly.

Fan settings deserve a thought too. With the fan set to run nonstop, air moving past the vents between heating cycles can feel cool in winter, and in summer it can blow some of the moisture the coil just removed back into the house. Many installers suggest the auto setting for most homes, but ask what suits your layout.

Routine care checklist

Most heat pump care is simple. Here is what homeowners can handle, and what to leave to a pro:

• Check the filter monthly and change or clean it on the schedule your system needs.
• Wash the reusable filters in mini-split indoor units as the owner's manual directs.
• Keep a couple of feet clear around the outdoor unit: no shrubs, stacked firewood or storage bins.
• Clear snow away from the unit after storms, and never chip ice off the coil with tools.
• Make sure the outdoor unit sits level and the indoor drain line is flowing.
• Schedule professional maintenance, commonly once or twice a year, since the system works in every season.
• Leave refrigerant, electrical and internal repairs to a licensed HVAC technician. Refrigerant work requires specific certification, and licensing rules vary by state.

Questions to ask before you buy or replace

A heat pump is a big decision, and a good installer will welcome questions. Consider asking:

• Did you do a load calculation for my house, or are you sizing from the old equipment?
• How will this system perform at the coldest temperatures we typically see here?
• What backup heat do you recommend, and when will it kick in?
• Is my ductwork in good enough shape, or does it need sealing or changes?
• Does my electrical panel have the capacity, or will it need work?
• Who pulls the permit, and will there be an inspection?
• Are there utility or state programs that apply here? These vary widely by location.

Getting to know your system

Once you understand that your heat pump is moving heat back and forth, its behavior stops being a mystery. HomeIsSecure publishes homeowner guides on heating and cooling, filter schedules and seasonal upkeep, so you can keep learning about the systems in your house before you ever need a repair.