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5 Different Types of Heat Pumps (Detailed Guide)

Photo collage of heat pumps for home; technician working on pump

Quicklist: Heat Pumps

  1. Reversible 
  2. Solid State
  3. Air-to-Air 
  4. Underwater/Underground 
  5. Hybrid 

We all know that comfort is an important part of life, but the reality is, most of us have price constraints on what we can afford. In addition, concerns about the environment leave us looking for more efficient ways to insulate ourselves from the external world.

The heating and cooling of our workplaces and homes are an important part of our lives. However, the impact of burning fossil fuels is becoming a huge issue that potentially threatens humanity. As such, an entire industry of people searching for alternatives is thriving.

While we wait for the cold-fusion heating systems of the future, there are some efficient alternatives already available today. Heat pumps are one of the most promising installation options replacing traditional heating and cooling systems.

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What Are Heat Pumps?

Modern heat pumps outside a home and covered in snow.

One of the biggest costs around both heating and cooling is the energy required to change the temperature of the air. If it is 90 degrees outside, energy must be used to reduce the temperature of the air inside so that you can have a cooler house.

The opposite is true for winter temperatures. One way to reduce the energy costs related to this process is to tap into a nearby location that remains cooler in the summer and warmer in winter.

In this way, the temperature may only need 10-15 degrees of change instead of 20-30 degrees. Heat pumps can accomplish this change by taking advantage of temperature differences between environments.

Take the case of the heating process in winter. A heat pump may use the warmer temperatures deep underground and move that heat from these sources into a home above ground.

This process still requires an external power source. Since temperatures underground do not vary as much as in open-air, this process saves the power needed to heat the air.

How Do Heat Pumps Work?

Diagram of how a heat pump work.

Generally speaking, most heat pumps contain a few main parts:

  • Condenser – A piece of equipment that condenses gas into a liquid. The process cools the material and allows the release of heat into the environment.
  • Expansion Valve – Regulates the flow of material injected into the evaporator.
  • Evaporator – Reverses the condenser by turning liquid into gas. This process causes the material to absorb heat from the environment.
  • Compressor – Reduces the volume of gasses and /or moves the liquid through the system.
  • Refrigerant – The liquid/gas moving through the system.

Basically, the system is designed to:

  • Condense the refrigerant in the pipes; releasing heat into the first environment.
  • Move the refrigerant into the second environment.
  • Then evaporate the refrigerant, absorbing heat from the second environment.
  • Compress the vapor, providing further heating by increasing internal pressure.
  • Move the refrigerant back to the first environment to restart the process.

This is generally the process used by refrigerators and air conditioners. However, a heat pump is designed to absorb heat from the warmer environment, and then release heat into the colder environment.

Brief History of Heat Pumps

As alluded to above, heat pumps have their origins in the process of refrigeration. The first recorded refrigeration process was created by William Cullen in 1748.

It took more than a century before Peter von Rittinger translated this technology into heat pumps by 1857. A second century later, the Royal Festival Hall in London created the first large-scale reversible heat pump.

In recent years, due to concerns about the environment, heat pumps are increasingly in use.

Types of Heat Pumps

In our modern heating and cooling industries, there are several kinds of heat pumps. This article will categorize them into three basic groups:

  • Air to Air
  • Underground/Underwater
  • Hybrid

1. Reversible Heat Pumps

Arrows shown on pipes of a heating System on the roof building.

Reversible heat pumps are capable of providing both heating and cooling processes using the same two environments. When heating, they use the external pipes to absorb heat and release that heat into the indoor environment.

When cooling, they absorb the heat from indoors and release that heat into the outside environment. Most heat pump types are available with the reversible option. 

Local climate needs may determine whether you need a reversible pump or one that is designed only to heat the indoors. Since reversible pumps are also more expensive, costs may influence which system is best for you.

However, some systems need extensive installation, such as underground or underwater types. These systems require one-half of the unit to be placed deep underground or at the bottom of a nearby body of water.

It may be more cost-effective in the long run to install a reversible system to avoid reinstallation costs later on.

2. Solid State

Insulated pipes for district heating.

While not generally in use to heat buildings, solid-state heat pumps do exist. Magnetic-based heat pumps use the properties of strong magnetic fields on certain metals. The fields tend to warm metals like iron or gadolinium up to 10 degrees Fahrenheit.

If the metal is then placed into an environment without the field, it will release extra heat into the environment. This process is not as energy efficient as systems using liquid or gas alternatives.

Thermoelectric pumps use voltage to transfer heat between two areas. These systems are also low-efficiency and have found little use outside small cooling devices.

Similarly, thermoacoustic devices have found little use outside cryogenic processes. These devices use relative pressure differences caused by acoustic waves to transfer heat energy.

3. Air-To-Air Heat Pumps

Heat pump outside a home in winter.

As the name implies, air-to-air heat pumps transmit heat from the open-air outside to the inside of the facility. They are available as reversible systems that can heat and cool indoor air.

The most common systems include those using vapor-compression, or hot water for radiators or direct human use. The kind using vapor compression operates similarly to refrigerators or air conditioners.

They involve a unit placed indoors, and connecting pipes to a unit placed above ground outdoors. Reverse Cycle Chillers operate in a similar fashion as other air-to-air pumps, except they cycle water instead of another vaporized refrigerant.

Once heated, the water can be moved through internal radiator systems. Both air-to-air and radiation systems are generally more energy-efficient than other heating systems. They are also cheaper to install than other forms of heat pumps because they are above ground.

Heat pumps can be safer for health since they do not involve the burning of carbon fuels. These substances can release carbon dioxide or nitrogen oxide as part of the burning process.

Air-sourced heat pump systems can be ideal for facilities in relatively temperate climates. They can provide sufficient heat in all but extremely cold weather approaching freezing temperatures.

Air-to-air heat pump systems do have a number of drawbacks. While they are great for temperate climates, they do not work well in climates with extremes. In freezing temperatures the heating capacity drops below tolerable levels.

Most systems include a form of resistance or oil-based emergency heating. However, emergency heating is not cost-effective or designed for constant use. Since systems are above ground, they can have problems with blockage.

Leaves, grass, snow, and ice can all impact the airflow and internal moving parts. Above-ground systems often require filters and defrosters. Air-sourced heat pump systems can require more up-front costs than other space heating solutions.

However, they can last 20 years or more and eventually save money in the long run. How long they take to recover upfront expenses depends on local electric and oil costs.

a. Mini-Split Heat Pump (Ductless)

HVAC Air Conditioner Compressor and a Mini-split system side by side outside a brick home.

The mini-split heat pump is an air-to-air operation designed for houses that do not have ducts. They are generally favored in retrofits to buildings formerly using hot water heaters or radiators.

Whereas traditional air-based heat pumps connect the external unit to the duct system, mini-splits use small openings cut into the side walls. The indoor units can be mounted on ceilings, walls, or the floor, up to 50 feet from the outdoor unit.

One mini-split external unit can be connected to up to four internal units. This allows effective zone heating and cooling since each internal unit can be controlled independently. However, installing the wrong-sized unit can lead to wasted energy or ineffectively heated rooms.

While some people may find the visible tubing and indoor unit unsightly, mini-splits tend to be more energy-efficient than duct systems. Ducts are notoriously inefficient, often losing large amounts of heat before reaching the vents.

b. Exhaust-Air Heat Pump

Air duct and ventilation system of a factory.

A final variant of air-to-air pumps is the exhaust-air heat pump. As the name describes, this version uses the exhaust from a building or manufacturing process.

Since the exhaust is typically warmer than the surrounding air, the same evaporation-to-condensation process can be even more effective. However, this process requires close access to consistent exhaust.

4. Underwater/Underground Heat Pumps

Heating system in the basement of a multi-story residential building.

Temperatures deep underground and underwater do not vary nearly as much as those in the open air. Because of this reality, this category of pumps can more efficiently provide both warmer and cooler air.

Some underground and underwater pumps use a dual line system. In this variety, a primary pipeline will run from an exchange box to the above-ground structure. A second pipeline will run from an exchange box to the underground/underwater maze.

The two pipes will meet inside the enclosed heat exchange box. Both underground and underwater systems can use a mixture of antifreeze and water to further prevent temperature extremes.

a. Water Source Heat Pumps

For structures close enough to deep water sources, underwater heat pumps may be an option. Water-based heat pumps work by a similar principle as air-based ones, except they use bodies of water as a medium for heat exchange.

They absorb heat from the water to warm the inside of the structure and release heat into the water to cool the structure. Some varieties also use water as a refrigerant, and water flows through a network of tubing as deep underwater as possible.

The temperature of the water inside the tubing will be warmed or cooled until it reaches the ambient temperature of the free-flowing water. The water in the tubes is then pumped up into the structure.

In the summer, the water will absorb heat from inside the facility, essentially cooling the structure. In the winter, the water will release heat into the colder interior.

Since temperatures deep underwater are relatively stable throughout the year, this system can be used in more extreme climates. This is a major advantage over air-based systems, which can only serve temperate climates.

Because there is no need for deep excavation, underwater systems are cheaper to install than underground systems. However, underwater systems can require significantly larger upfront costs than air-based mechanisms.

Of course, the biggest drawback of underwater heat pumps is the requirement of being very near a body of water. While external wells can work, larger bodies with free-flowing water would be more effective.

Underwater systems can be closed loops or open loops. Much like the other varieties discussed, closed loops move a refrigerant through a closed pipeline.

Open loops, on the other hand, collect open water into the system and move that water through the internal structure. Heat is then released or absorbed as necessary. The water is then released back into the environment in a different location.

Because this is dealing with plain water from the environment, this process carries the additional risk of mineral deposits inside the line. These deposits can interfere with the flow of water, and thus reduce the efficiency of the system.

b. Ground-Source Heat Pumps

Illustration of a ground source heat pump.

Also called Geothermal Heat Pumps, these systems use the constant temperatures deep underground to heat or cool structures. Like deep-water pumps, these often use water as the refrigerant and do not require a condensation/evaporation process.

However, standard condensation and evaporation varieties exist as well. As with deep-water versions, the water refrigerant type uses a network of pipes deep underground.

The water flows through the pipes, releasing or absorbing heat until it matches the ambient temperature of the ground. The water is then pumped into the above-ground structure to release or absorb heat as needed.

While deep-water pipes typically lay horizontally against the bottom of the water, underground types have a number of configurations. Where horizontal space is limited, pipes can lay in vertical loops. A number of deep holes are drilled into the ground.

The pipes form a chain of deep vertical u-shapes. Each of the drill holes can be filled with groundwater or some other medium to better facilitate the temperature exchange.

Where there is more space, the pipes can be arranged in a horizontal network of u-shapes laying on a single plane below the frost line. The ground can be excavated and then replaced to cover the pipes.

Horizontal pipes can also be arranged radially, with a process called horizontal directional drilling. This process is favored because it can be installed without disturbing driveways and other surface features.

5. Hybrid Heat Pumps

Solar Water Panels Heating System

The biggest problem with pure heat pump designs is providing sufficient heat in very cold climates. Air-to-air pumps cannot consistently work effectively at or below freezing temperatures. This leaves systems using costly emergency heat for extreme cold.

Geothermal and underwater systems are much better at cooling than heating. Temperatures deep underground/underwater can reach between 50 to 60 degrees Fahrenheit. That temperature is much better at cooling a hot room than heating a freezing room.

Accordingly, a number of hybrid heat pumps exist to assist in the heating process. These pumps operate as air-source pumps that use additional energy sources to provide extra heat to be released indoors. Examples include:

  • Gas-Fired Heat Pumps use natural gas as the heat source, providing additional warmth in cold climates. This version can also use an ammonia-water refrigerate process to provide both heating and cooling.
  • Solar-Powered Heat Pumps can use solar panels as a source of power to drive and heat the system. They can also use direct sunlight as an additional heat source.

USA Climate Zones

USA Climate Zones Graphic

Different climate zones require different amounts of energy (measured in British Thermal Units) to heat (or cool) homes. In a cold climate, a 2,500-square-foot home may need a heating system with approximately 150,000 BTU capacity.

homestratosphere.com

Best Type Heat Pump For Various Purposes

Cold Climate

A heat pump outside the house during winter.

When it comes to keeping your home warm when you live in a cold climate, you actually have two great options to choose from. Although both types of heat pumps are good, the one you choose will depend on your own unique needs and your budget.

Centrally ducted heat pumps look like central air conditioners because they come with indoor units and a coil that goes inside your home’s ductwork. You can use a central duct heat pump during the summer as an air conditioner thanks to a fan that moves air over this coil.

For non-ducted heating systems (such as hydronic hot water heat) you can go ductless with a mini-split heat pump. It operates like a centrally ducted heat pump but doesn’t use ductwork and comes with an outdoor unit and indoor heads. Keep that in mind because all these units will have to be installed, preferably by professionals.

These indoor heads come with fans built-in that can help the heat pump act as an air conditioner during the warmer months. In general, mini-split heat pumps tend to be the best heat pump option for cold climates.

Warm Climate

Heating a home in a warm climate isn’t necessarily easier than in a cold climate. The winters still get pretty cold, after all. There are two main heat pump options you can choose from, and they’ll work well at keeping your home nice and warm in the winter.

The first option, a ducted air-source heat pump, acts and appears a lot like central air conditioning. You get an indoor and outdoor unit, and they both have aluminum fins and coils that will collect or release heat and transport it between them.

Your second option is a mini-split air-source heat pump, which is also known as a ductless air pump. These systems don’t rely on ductwork to move the warm air throughout the home. Instead, it will be connected to indoor heads that will help distribute the heat. 

There are other types of heat pumps you can use as well, though they may not be as efficient. This includes geothermal heat pumps, air-to-water heat pumps, and water-source heat pumps.

Large Home

A heat pump outside a house.

If you have a large home to heat up during the winter, electric heaters may sound like a nightmare because they can be really costly to keep on and they pose a safety risk to your family.

There are three main options for the owners of large homes when it comes to the best types of heat pumps. You can choose between air-source heat pumps, ground-source heat pumps, and water-source heat pumps.

The air-source heat pumps (perhaps better known as air-to-air heat pumps) extract heat from outdoor air and bring it into the home. 

Ground-source heat pumps — also called geothermal heat pumps — extract heat energy from the soil and ground around your home’s foundation, which it then transfers into your house. They operate rather quietly and are very reliable, more so than air-source heat pumps.

Water-source heat pumps are only really an option if your house is located near a body of water such as a pond. The system will extract heat energy from the water and then distribute it throughout the home. These heat pumps may require secondary heat sources to serve as a backup.

Efficiency

Heating your home in the winter is not a luxury — it’s a necessity. But, unfortunately, because heating can be so expensive, it feels like a luxury.

That’s why it’s important to find the right kind of heat pump that will work well and save money at the same time. The two best options are mini-split heat pumps (ductless heat pumps) or underground heat pumps.

Mini-split outdoor units can be used to power several indoor units and the heat can then be controlled independently. They can be more energy-efficient than other options when they’re used along with smart AC controllers.

Underground heat pumps can provide an almost-constant temperature at all times of the year. They are much more energy-efficient for this reason, as well as thanks to the fact that they don’t use a lot of energy to stay operational.

These two types of heat pumps are typically the most energy-efficient options and you can choose either one and get great results.

Top Brands of Heat Pumps

Armstrong Air

Armstrong Air heat pump.

  • Efficiency rating: 15-20 SEER
  • Unit price range + installation: $4,650- $12,400

Armstrong Air is an Ohio-based HVAC manufacturer, and a subsidiary of Lennox Furnace Company, an equally-coveted HVAC brand. The Armstrong heat pump lineup has only five models; the 4SHP20LX, 4SHP16LS, 4SHP16LE, 4SHp15LE, and 4SHP14LB.

They have variable features, and price tags but generally include features like variable capacity performance to adjust cooling in increments, and two-stage performance to allow two different output speeds for heating and cooling conversely ensuring maximum comfort.

Armstrong heat pumps often have variable efficiency ratings ranging between 15 and 20 SEER. They are also often equipped with high and low-pressure switches, and you get a 10-year warranty regardless of the model you purchase.

The brand’s top heat pump models come with a lifetime warranty, and four of its six models are energy-certified. Armstrong Air’s heat pumps downsides? Well, their lineup has quite a few options to select from, and only top models have high SEER ratings.

Bryant

Bryant heat pump.

  • Efficiency rating: 14-20 SEER
  • Unit price range (installation included): $5,200- $10,6200

Bryant is one of the oldest companies in the HVAC industry, having been first established in 1904. So, it’s no surprise that they’re also among the top heat pump brands. They have a solid lineup of heat pumps divided into the following categories: Evolution Preferred and Legacy.

The Evolution series features the brand’s best heat pumps. They have a variable speed compressor, energy efficiency ratings of up to 24 SEER, and an HSPF of up to 13. This makes models in this category perfect for regions with extreme winters because they don’t require a backup heating system.

Additionally, buyers earn up to $1,300 in rebates. For mid-level buyers, Bryant’s Preferred series is the way to go. They feature single and two-stage compressors, sound levels as low as 70Db, SEER ratings between 17 and 18, and a 9.5 HSPF.

When money is tight but you need a quality heat pump, Bryant’s Legacy line features fantastic options such as the Legacy Single Stage heat pump. It has a cooling efficiency rating of 15SEER, 8.9HSPF, a single-stage compressor, and is remotely accessible with the Bryant Housewife app.

Bryant offers a 10-year limited warranty standard with all its heat pumps, but you have the option to extend it. Note that, in addition to being among the most popular, Bryant is also considered one of the best heat pump brands.

This is thanks to their excellent consumer-focused programs such as the Factory authorized Dealers program through which only a select number of dealers are allowed to sell heat pumps. The dealers are also offered heat pump installation training to ensure the utmost quality.

Goodman

 Goodman heat pump.

  • Efficiency rating: 15.2-18 Seer
  • Unit price range (installation included): $4,995-6,100

Wondering what top heat pump brand is the most affordable? Checkout Goodman. Goodman is one of the best HVAC brands in the country, and a member of Daikin Industries, a Fortune 1000 HVAC company. We only found eight products in their heat pump lineup.

All except the GVZC20 had a SEER rating between 15.2 and 18. The GVZC20 is a top-line model with a cooling efficiency of 21 SEER and 10HSPF, making it ideal for buyers in extreme weather conditions.

Goodman heat pumps are generally affordable, and all feature louvered coil guards to prevent coil damage, filter driers to absorb residue, and contractors with lugs for seamless installation and wiring.

While most brands transition to aluminum to reduce manufacturing costs, Goodman heat pumps still spot copper coils which are easy to repair, and cheaper to replace.

The brand uses a proprietary suction accumulator technology for all its compressors. This prevents refrigerant accumulation in the suction lines resulting in a seamless flow of air in and out of the unit and consequently enhancing its lifespan.

And to inspire confidence in this technology, Goodman offers a lifetime compressor warranty for its heat pumps.

Rheem

  • Efficiency: up to 20 SEER/11.0HSPF
  • Unit price range (unit only): $1,400-$3,200

Rheem is a privately held residential and commercial HVAC company under Paloma Industries (that means they’re affiliated with RUUD, another top heat pump brand). The company began as a water heating system manufacturer in 1925 and expanded into HVAC two decades later.

Today, they offer a wide variety of heat pumps, categorized into three main series; Classic, Classic Plus and Prestige. If you are on a tight budget, check out the Classic series. It features affordably-priced models with a capacity between 1.5 and 5 tons.

They are also usually equipped with either single, or multi-stage scroll compressors, and have an efficiency rating between 14.5 and 16 SEER.

The Classic Spot series is the sweet spot between cost and additional performance. It includes heat pumps with a 2-5 tons capacity, three-stage scroll compressors, and an efficiency of up to 18 SEER. For Rheem flagship models, browse the Prestige series.

You’ll shell out some extra bucks, but you’ll get heat pump options with variable compressor speeds, and efficiency ratings of up to 20SEER/11HSPF. Note, all Rheem heat pumps often feature a scroll compressor for silent performance, and come with a standard 10-year warranty. A majority also boast smart and advanced controls.

Where To Buy Heat Pumps

Heat pumps are no longer considered novel pieces of equipment and today, heat pumps can be purchased wherever heating and cooling systems are sold.

Air-to-air systems are generally much cheaper and easier to install, however, they are the least efficient form of the heat pump. Underground or underwater heat pump systems are much more efficient. They require extensive installation, since they must be placed underground, and also require additional piping to move the refrigerant a longer distance.

If after evaluating every important factor (size, climate, compressor type, efficiency etc.) you’ve made up your mind to invest in one, here are some options on where to buy heat pumps:

From E-Commerce Retailers

Nowadays you can buy almost anything online, and heat pumps are no exception. E-commerce retailers like Amazon are an excellent option when you need a variety to select from or need to compare prices because they stock heat pumps across all brands.

Other excellent e-commerce retailers to check out for heat pumps include Walmart, Best Buy, and Home Depot. But before you purchase a heat pump from an e-commerce retailer ensure you consider:

The price

E-commerce platforms like Amazon liaise with individual third-party sellers to ensure consumers have a wide variety of merchandise to select from. Consequently, you’ll often find the price quoted on individual heat pumps are a little higher than what’s originally offered by the manufacturer.

While the e-commerce platform’s occasional offers help subsidize the cost, ensure you compare prices as offline or direct brand dealers might be more affordable.

Warranty Activation Process

A majority of heat pumps in the market come with a standard 10- year limited warranty, and a five-year compressor guarantee.

However, you’ll find that you have to register with the manufacturer to activate the warranty. If you decide to buy one from e-commerce retailers ensure you find out about the warranty activation process beforehand.

Installation and Servicing

Most e-commerce retailers will sell you and deliver the heat pump unit, but what about installation? In most instances, you’ll have to find a technician yourself. However, some e-commerce retailers may have an installation program in place.

For instance, Amazon offers complete in-home installation and assembly for select products. Eligible products often feature an expert installation option and cost details on the product detail page. When it comes to servicing, Amazon has the HVAC Pros program.

Sadly, not every e-commerce retailer has such options. So, ensure you consult on installation and servicing regardless of the e-commerce retailer you buy your heat pump from.

From Affiliate Marketers

Affiliate marketers are entrepreneurs (mostly influencers) who earn a commission by promoting a product or service sold by other retailers, or directly by manufacturers.

The affiliate marketer creates content regarding that particular product, or service enlightening the buyer on its best features, pros, and cons. Additionally, they provide an affiliate link through which buyers are redirected to the sales page.

Why Buy a Heat Pump Through Affiliate Links?

Affiliate marketers are a good option when you are a first-time buyer with no idea how a product works.

For instance, when it comes to heat pumps, an affiliate marketer will not only break down how heat pumps work and the different varieties, but they’ll also conduct market research on your behalf, and recommend top heat pump brands and models based on metrics like SEER and HSPF ratings, compressor type and other key features.

However, while buying a heat pump through affiliate links be sure to do due diligence on every recommended item. This is because some affiliate marketers will often recommend any product as long as they earn a commission.

Directly From Manufacturers

If e-commerce retailers and affiliate marketers do not tickle your fancy, buy heat pumps directly from manufacturers. Nearly all HVAC manufacturers nowadays have a sales page from which you can order.

Buying directly from the manufacturer means no middlemen are involved, resulting in lower prices. You also get a direct line of communication resulting in direct, and ongoing support.

That means if the manufacturer does not offer installation, they may recommend some of the top contractors in their network, resulting in quality heat pump installation, and servicing.

However, note, most manufacturers may require a minimum quantity order which renders this option unfavorable if you’re only buying one unit.

You may also have to go through lengthy buying processes as most manufacturers have sale policies geared towards bulk buyers. Check out your favorite heat pump brand website to determine if buying direct is a viable option. Some brands to prioritize in your search include:

  • Goodman
  • Coleman
  • Rheem
  • Dakin

Authorized Local Contractors

Authorized local contractors are another excellent option when you’re looking to buy a heat pump. They often buy directly from the manufacturer.

Because they are authorized, work directly with manufacturers and buy in bulk, these contractors typically offer either original prices or mark them up only slightly resulting in manageable costs for the buyer.

Buying a heat pump from a local contractor also means direct access to them and consequently, ongoing support.

More importantly, local contractors offer comprehensive services meaning they don’t just sell you the unit, they also offer installation and long-run maintenance which means convenience for you.