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What is a Heat Pump? 12 quick and easy Facts

Is getting a heat pump going to be one of the best decisions you’ve ever made for your house? You might be able to answer this question, after getting to the end of this article.

Heat pumps use electricity to transfer heat from one place to the other. The biggest benefits of these systems are that they are energy-efficient and much more eco-friendly than regular ACs and furnaces, and that one system can both cool and heat your house.

Want to find out more about these cool units? We present to you our carefully curated guide – ‘Heat Pump – Everything You Need to Know’.

What Is a Heat Pump?

A heat pump can become a part of a heating and cooling system that is installed outside the house. Instead of burning fossil fuels, heat pumps work by using electricity.

The units do not produce heat, they transfer it. 

One single system can handle both heating and cooling. As a result, the homeowner might not need to install two separate units.

Fun fact: the first heat pump was built in 1856. Back then, the unit was used to dry salt in salt marshes. 

How Does a Heat Pump Work?

Heat naturally wants to move to a cooler space that has less pressure. This is the basic ‘law’ that allows the heat pump to work its magic.

What Are the Components of a Heat Pump System?

The major components of a heat pump system include:

What is a heat pump and how it works
  • The outdoor unit with a coil. This part can act either like a condenser, or like an evaporator (in cooling and heating mode respectively).
  • The indoor unit with a coil and a fan.
  • The refrigerant (can absorb and release the heat).
  • The compressor (enables the flow of the refrigerant).
  • The reversing valve. The main job of this component is to change the direction of the flow of the refrigerant, which makes the system switch from heating to cooling mode and back again.
  • The expansion valve regulates the flow and temperature of the refrigerant through the system. 

Cooling mode

  1. Liquid refrigerant gets pumped to the indoor coil. The warm air from the house is then blown across the coils (the refrigerant absorbs the heat, heats up, and turns into gas).
  2. During this process, cool air is produced. It gets pushed out of the system through the ductwork and into the rooms.
  3. The refrigerant that is now gaseous passes through the compressor which causes the refrigerant to heat up even more. It continues to move to the outdoor coil.
  4. Outside air gets moved across the coils of the outdoor unit via a fan. At the moment, the outside air is cooler than the gaseous refrigerant that has been heated up, so the heat from the refrigerant gets transferred to the outside air.
  5. As the refrigerant cools down, it turns back into a liquid (but it’s still quite warm). It then gets pumped back to the expansion valve in the indoor unit.
  6. The expansion valve reduces the pressure of the refrigerant. This process turns the refrigerant back into a cool liquid.
  7. The cycle is ready to be repeated.

Heating mode

The reversing valve reverses the flow of the refrigerant. In heating mode, the cycle stays the same but works in the other direction.

The outside air now becomes the heating source (even if the temperatures outside are very low). The coil in the outside unit functions as an evaporator and the one in the inside unit ‘becomes’ the condenser.

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The heat energy gets absorbed by the liquid refrigerant that then turns into a cold gas. The system applies pressure to the refrigerant to turn it into a hot gas. 

After that, the gas gets cooled in the indoor unit, heating the air that is then going to be transferred into the house. At this point, the gas turns into a warm liquid.

The liquid enters the outdoor unit and then gets relieved of pressure. Finally, we have a cool liquid that can be used in the cycle once again. 

Read: What Is The Most Efficient Heating And Cooling System?

What Are the Types of the Heat Pump?

Though they all operate on the same principles, there are many of types and sub-types of heat pumps. Let’s begin our discussion with the three main categories: air, water, and ground.

3 types of heat pump drawing

Depending on the medium for heat exchange that the systems use, there are three different types of heat pumps:

  • Air-source heat pumps, for example, use outside air and are great for areas with a moderate climate.
  • A water source heat pump requires the house to have a body of water near it.
  • A geothermal (ground-source) heat pump takes advantage of the underground temperatures that stay relatively constant throughout the whole year.

The sub-types of the heat pump systems include:

  • A hybrid heat pump is a great option for the areas that experience warm summers and extremely cold winters. Homeowners can combine two different types of heat pumps to boost efficiency (for example, a ground and air-source heat pump combination).
  • A solar heat pump is installed together with an air source or geothermal system. This allows the homeowner to integrate solar panels into the system and get the unit working without electricity. 

Finally, there are different ways of installing heat pumps:

  1. A ducted system – a common option for the houses that already have existing ductwork. The outdoor unit will be placed in a large metal box and the indoor unit can be placed in the attic, basement, or even closet.
  2. A mini-split ductless system is a great choice for homes that don’t have ducts. This is often a good choice for a retrofit scenario.

Let’s take a closer look at some of these types of heat pumps. 

How Does a Mini Split Heat Pump Work?

Lennox mini split heat pump with two heads

If your home doesn’t have ductwork, then going for a mini-split heat pump might seem like the most obvious choice.

Such a system has an outdoor and an indoor unit that are connected via a refrigerant line. 

If you want to control the temperature across the entire house, you should opt for a system with a few indoor units. Some mini-splits come with a few outdoor units that are connected to a single indoor unit each (but such models are less common).

Mini-splits are more efficient than conventional heat pumps for a number of reasons.

Due to the fact that mini-splits do not require ductwork, they are not impacted by air leakage associated with ducts. Also, many of units have an integrated variable speed technology which facilitates even greater efficiency.

Such a heat pump will work great in older homes that are not equipped for the installation of ductwork, in historic homes where the homeowners can’t afford to change the structure of the house, and in-home add-ons that are not connected to the main ductwork.

Of course, a mini-split heat pump can become a wonderful heating and cooling solution for practically any home, but do bear in mind that every room might require a separate indoor unit.

Moreover, even though modern heat pumps are extremely effective, experts still recommend having a backup plan for those extra cold days, when the heat pump might fail to get the job done. 

How Does a Geothermal Heat Pump Work?

types of Geothermal layouts

Geothermal heat pumps can reduce electricity use by up to 60%! Moreover, these systems can also help you control the humidity levels in your house. 

The thing that makes geothermal heat pumps different from all the other systems is that they are coupled to the ground, not the air. 

The temperature around 10-feet below ground is relatively constant. Unlike other heat pumps that might struggle to warm the air during the cold season, geothermal heat pumps will not experience such a problem.

In Maryland, for example, the below-ground temperature is a constant 57 degrees.

There are two types of geothermal heat pumps – closed-loop and open-loop systems.

The latter is a good choice for the areas that have a lot of water that is low in minerals. Such systems will be using groundwater from the well.

A closed-loop system works by circulating a water-based solution through underground pipes. The loops can be vertical or horizontal, and if there is a body of water next to the house, then a pond loop can be used. 

For a deeper dive into geothermal, read: What is Geothermal Heating?

How Does a Two-Stage Heat Pump Work?

A two-stage (or dual-stage) heat pump has a two-stage compressor. That means that the system has two levels of intensity and that it doesn’t have to always work at its full capacity to keep your house warm or cool.

The majority of the year, the heat pump is going to operate at a low speed. But once it gets too hot or too cold, the system is going to switch to its high-speed mode to keep up.

You don’t have to change the speed manually; the heat pump will automatically change the stage according to the desired temperature set on your thermostat. 

Such a two-stage system makes the heat pump much more effective and, as a result, saves you quite a lot on energy bills. Moreover, such units will keep the temperature in your house constant year-round, allowing you to forget about the annoying cold or hot spots. 

How Does a Heat Pump Water Heater Work?

A heat pump can be used not only to cool or heat your home. You can also use it to heat water.

Just like regular heat pumps, water heaters do not create heat, they just move it. But in this case, the unit is going to transfer the heat to a storage tank with water.

You can buy a stand-alone device that is going to have only one job (water heating) or you can go for an air-source heat pump that will be heating and cooling your house and also heating the water.

Do bear in mind that such devices can’t operate efficiently in cold spaces. So, putting them in a room that is always warm (for example, a furnace room) is the right decision, so the system will work effectively.

Ideally, water heaters should be installed in rooms that remain in the 40-90 F range all year round. The devices should also have enough air around them – at least 1.000 cubic feet.

For more info, read: What is a Water Heater Heat Pump?

How Does a Heat Pump Dryer Work?

Did you know that you can use a heat pump system to dry your clothes?

A heat pump dryer is a closed-loop system. It removes moisture from the clothes with the help of heated air and then uses this moisture in the system.

Such dryers reduce energy consumption by around 28% and are much gentler on clothes as the unit is able to remove moisture at low temperatures

Another important benefit – compact models do not require a vent. That means that they can be installed in any space that has a water source and electricity. 

Do bear in mind that once the evaporator removes the moisture from the clothes, the water needs to be drained. You can choose to manually drain the water tank, use a drain hose, or install a special device that connects the dryer to the washer’s drain.

How Does a Swimming Pool Heat Pump Work?

Such heat pumps use outside air to extract the warmth out of it and then circulate the heat through the coils.

The water from the swimming pool is pushed through a filter and the heat pump.

When the refrigerant and the pool water ‘meet’ in the heat pump system, the hot gas transfers its heat to the water that is then pushed back into the pool.

The water that had passed the system will be heated by around 3-5 degrees. Generally, A swimming pool heat pump will work effectively while the temperatures stay above 45 F.

Fact: An air conditioner moves 2-3 units of heat from your house for every 1 unit of electricity it consumes. A swimming pool heat pump delivers 5-7 units of heat to the pool water for every 1 unit of electricity consumed.

How Does a Heat Pump Thermostat Work?

Understanding how your thermostat works is incredibly important. If you know how to use this smart device, you’ll be able to save a significant amount on your energy bills and the temperature in your house will always be spot on.

The first thing that you should bear in mind is that a heat pump needs a thermostat that is specifically designed for heat pumps. That is because the system controls both heating and cooling and the thermostat needs to have a connection with the reversing valve, in order to be able to change the direction of the refrigerant’s flow. 

In a nutshell, an air conditioner’s thermostat requires only 4 wires, while a heat pump’s thermostat would need a fifth one.

Tip: The reversing wire usually has a brown color.

Another thing that you should check before getting a thermostat is whether or not your heat pump has an emergency/aux heating option. If it does, then you should choose a thermostat that supports such a mode.

The emergency heating option kicks in when it gets freezing cold outside. In such conditions, a lot of heat pumps are going to struggle to keep your home nice and toasty.

But if the unit has an emergency/aux heating option, it will be able to heat the house even in extreme cold (however, the mode is not energy efficient at all).

Read: Why Does The Room Temperature Not Match The Thermostat Setting?

How Does a Heat Pump Work with a Furnace?

If you reside in a winter climate characterized by severe cold, relying solely on a heat pump might not suffice.

Certain heat pumps are equipped with a heat strip capable of generating the extra heat needed when temperatures plunge below 40°F. However, opting for this feature can significantly escalate your energy expenses.

Instead of a heat strip, you can go for a backup plan – something called ‘a dual-fuel HVAC system’. These are very common in modern homes.

Connecting your heat pump to an electric, gas, or oil furnace can be a game-changer for extreme cold situations. This integrated system adeptly switches between the two energy sources whenever the weather demands it.

Typically, homeowners face the decision of either replacing their air conditioner with a heat pump or enhancing their heat pump setup by adding a high-efficiency furnace.

Read: Do I Need A Furnace With A Heat Pump?

How Does a Heat Pump Work in Summer?

heat pump operation in summer and winter

During the hotter time of the year, your heat pump is going to be extracting heat from its coils (heated by outside air) and pushing the leftover cooler air into your house via the indoor unit.

A fuller explanation can be seen here: Heat Pump Cooling Efficiency In Hot Weather

How Efficient is a Heat Pump in the Winter?

In the winter, the heat pump is going to pull the heat out of the outside air and transfer it into your house. But how on earth will that work, if the air gets freezing cold?

The reality is that heat pumps maintain the ability to draw heat from the air even in extremely cold temperatures. However, certain models may experience reduced efficiency during colder months, underscoring the importance of having a furnace as a backup.

Another thing to bear in mind – during winter your heat pump system can go into defrost mode. It is absolutely normal and you’ve got nothing to worry about.

The defrosting cycle typically lasts around 10 minutes. During this period, the system eliminates ice that has accumulated on the outside unit and then resumes regular operation.

If your system frequently enters defrost mode, consider changing the filter and cleaning the external unit. Additionally, a refrigerant leak or a malfunctioning thermostat could be contributing factors, making it advisable to seek the assistance of a technician in such situations.

Do You Really Save Money with a Heat Pump?

There are two ratings that you have to pay attention to when choosing a heat pump:

  1. The HSPF indicates the system’s heating efficiency. Look for the unit that has a rating of 8-10.
  2. The SEER indicates the system’s cooling efficiency. The rating can go as high as 23.0; the higher the rating, the more money you’ll be able to save.

To go the extra mile, you can get yourself a two-stage or a multistage heat pump that increases the efficiency levels even more.

In general, an air-source heat pump will help reduce your energy bills by 50% and a geothermal system can reduce energy use by 30-60%.

How Much Does a Heat Pump Electric Bill Cost?

If you have been using a gas or an oil furnace before, then your electricity bills are going to rise, as soon as you install a heat pump.

But that is absolutely ok, as you will be able to save on the cost of the actual fuel.

Heating your home with a heat pump will, on average, cost you 48% less than when heating with an oil furnace, and around 66% less than all-electric. Of course, exact savings will depend on factors such as fuel costs and electricity costs in your area.

And if you manage to pair your heat pump with solar panels, then you could possibly further reduce the bills by around 40% of what’s left.

Are Heat Pumps Worth It?

Heat pumps are an amazing option for heating and cooling, but they are not perfect.

Here are a few disadvantages that you should be aware of:

  • High upfront costs: Even though heat pumps will help you save in the long run, their initial cost is quite high. The cheapest systems are the mini-splits (prepare to pay over $1,500); geothermal heat pumps are considered to be the most expensive ones due to high installation costs (up to $36,000).
  • Some heat pumps are incredibly challenging to install: Local geology, the movement of heat, and many other factors have to be taken into consideration.
  • Some heat pumps experience issues in cold weather: In freezing temperatures, the full heat pump’s efficiency can’t really be reached. However, this problem might become non-existent, if you choose to invest in an upgraded system.

Other than that, heat pumps are a truly efficient way to heat and cool your house. Moreover, such systems consume fewer resources, so…. why not give this energy-efficient alternative to ACs and furnaces a try?