An air-source heat pump can provide efficient heating and cooling for your home. When properly installed, an air-source heat pump can deliver up to two to four times more heat energy to a home than the electrical energy it consumes. This is because a heat pump transfers heat rather than converting it from a fuel, like combustion heating systems.
Air-source heat pumps have been used for many years across the United States. Recent advancements in technology have made them a viable heating alternative even in regions with extended periods of subfreezing temperatures.
For example, a study by the Northeast Energy Efficiency Partnerships found that when units designed for colder regions were installed in the Northeast and Mid-Atlantic regions, annual savings were around 3,000 kWh (or $459 at $0.153/kWh) compared to electric resistance heating, and 6,200 kWh (or $948 at $0.153/kWh) compared to oil systems. When displacing oil, the average annual savings are nearly 3,000 kWh (or about $300).
A heat pump's refrigeration system consists of a compressor and two copper or aluminum coils (one indoors and one outside) with aluminum fins to aid heat transfer. In heating mode, heat energy is extracted from the outdoor air and brought into the house via a compressor circulating refrigerant. A reversing valve changes the direction of refrigerant flow for cooling and for the winter defrost cycle. In warmer months, heat is extracted from the home and rejected outdoors.
Today's air-source heat pumps are more efficient due to several technical advances:
When choosing an air-source heat pump, it's essential to understand the different configurations available. These systems can be tailored to suit various home layouts, preferences, and heating and cooling needs. Here's an overview to help you make an informed decision:
Every residential heat pump sold in the United States has an EnergyGuide label displaying its heating and cooling efficiency ratings.
In general, the higher the HSPF and SEER, the higher the cost of the unit. However, the energy savings can return the higher initial investment several times during the heat pump's life. A new central heat pump replacing a vintage unit will use much less energy, substantially reducing air-conditioning and heating costs.
As of January , more stringent efficiency terms (HSPF2 and SEER2) were enacted to better reflect airflow resistance due to more realistic duct systems. For example, a unit rated at 15 SEER would be a 14.3 SEER2. Likewise, an 8.8 HSPF would equate to a 7.5 HSPF2 heating efficiency.
These are some other factors to consider when choosing and installing air-source heat pumps:
To choose an electric air-source heat pump, look for the ENERGY STAR® label. In warmer climates, SEER is more important than HSPF. In colder climates, focus on getting the highest HSPF feasible.
Heat pumps can experience issues with poor airflow, restrictive or leaky ducts, incorrect refrigerant charge, and improper wiring of electric resistance auxiliary heat strips. To ensure your heat pump operates efficiently and to avoid these performance issues, it’s essential to hire a qualified technician.
Consumers should seek out technicians certified by programs recognized under the DOE’s Energy Skilled Heat Pump Programs. This program identifies organizations that certify technicians and training programs for heat pumps, ensuring the technician has the necessary expertise to install and service the system correctly.
Finding a skilled, knowledgeable contractor is one of the most important steps to ensure the long-term performance of your HVAC equipment. It’s also one of the biggest barriers for consumers, after first cost. Be sure to hire someone certified by a recognized program to get the most out of your heat pump system.
Air-source heat pumps provide efficient and effective heating and cooling for homes in various climates. By selecting the right type and ensuring proper installation, you can enjoy significant energy savings and improved comfort.
For more information and to find ENERGY STAR certified air-source heat pumps, visit the ENERGY STAR website. Ensure your system is installed correctly and maintained regularly to maximize efficiency and savings.
To find technicians certified under the DOE Energy Skilled Heat Pump Programs, visit the DOE Energy Skilled Heat Pump Programs page. Choosing a certified technician ensures proper installation and maintenance, helping to avoid performance issues and achieve long-term energy savings.
The two most common types of heat pumps are air-source and ground-source. Air-source heat pumps transfer heat between indoor air and outdoor air, and are more popular for residential heating and cooling.
Ground-source heat pumps, sometimes called geothermal heat pumps, transfer heat between the air inside your home and the ground outside. These are more expensive heat pump installations but are typically more efficient and have a lower operating cost due to the consistency of the ground temperature throughout the year.
How does a heat pump work? Heat pumps transfer heat from one place to another by different air or heat sources. Air source heat pumps move heat between the air inside a home and the air outside a home, while ground source heat pumps (known as geothermal heat pumps) transfer heat between the air inside a home and the ground outside a home. We will focus on air source heat pumps, but the basic operation is the same for both.
Despite the name, heat pumps do not generate heat – they move heat from one place to another. A furnace creates heat that is distributed throughout a home, but a heat pump absorbs heat energy from the outside air (even in cold temperatures) and transfers it to the indoor air. Learn more about heat pumps vs furnaces.
When in cooling mode a heat pump and an air conditioner are functionally identical, absorbing heat from the indoor air and releasing it through the outdoor unit. Click here for more information about heat pumps vs air conditioners.
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When considering which type of system is best for your home, several important factors should be considered, including the size of the home and the local climate. A local Carrier dealer has the expertise to properly explain heat pumps, evaluate your specific needs and help you make the right decision.
Homeowners in need of a new heating or cooling system, may consider the type of climate they live in before purchasing a heat pump system. Heat pumps are more common in milder climates, where the temperature does not typically drop below freezing. In colder regions, they can also be combined with furnaces for energy-efficient home heating on all but the coldest days. When the temperature outside drops too low for the heat pump to operate effectively, the system will instead use the furnace to generate heat. This kind of system is often called a dual fuel system – it is very energy efficient and cost effective.
A typical air source heat pump system consists of two major components, an outdoor unit (which looks just like the outdoor unit of a split-system air conditioning system) and an indoor air handler unit. Both the indoor and outdoor unit contain various important sub-components.
The outdoor unit contains a coil and a fan. The coil operates as either a condenser (in cooling mode) or an evaporator (in heating mode). The fan blows outside air over the coil to facilitate the heat exchange.
Like the outdoor unit, the indoor unit, commonly referred to as the air handler unit, contains a coil and a fan. The coil acts as an evaporator (in cooling mode) or a condenser (in heating mode). The fan is responsible for moving air across the coil and throughout the ducts in the home.
The refrigerant is the substance that absorbs and rejects heat as it circulates throughout the heat pump system.
The compressor pressurizes the refrigerant and moves it throughout the system.
The part of the heat pump system that reverses the flow of refrigerant, allowing the system to operate in the opposite direction and switch between heating and cooling.
The expansion valve acts as a metering device, regulating the flow of the refrigerant as it passes through the system, allowing for a reduction of pressure and temperature of the refrigerant.
Heat pumps do not create heat. They redistribute heat from the air or ground and use a refrigerant that circulates between the indoor fan coil (air handler) unit and the outdoor compressor to transfer the heat.
In cooling mode, a heat pump absorbs heat inside your home and releases it outdoors. In heating mode, the heat pump absorbs heat from the ground or outside air (even cold air) and releases it indoors.
One of the most important things to understand about heat pump operation and the process of transferring heat is that heat energy naturally wants to move to areas with lower temperatures and less pressure. Heat pumps rely on this physical property, putting heat in contact with cooler, lower pressure environments so that the heat can naturally transfer. This is how a heat pump works.
STEP 1
Liquid refrigerant is pumped through an expansion device at the indoor coil, which is functioning as the evaporator. Air from inside the house is blown across the coils, where heat energy is absorbed by the refrigerant. The resulting cool air is blown throughout the home’s ducts. The process of absorbing the heat energy has caused the liquid refrigerant to heat up and evaporate into gas form.
STEP 2
The gaseous refrigerant now passes through a compressor, which pressurizes the gas. The process of pressurizing the gas causes it to heat up (a physical property of compressed gases). The hot, pressurized refrigerant moves through the system to the coil in the outdoor unit.
STEP 3
A fan in the outdoor unit moves outside air across the coils, which are serving as condenser coils in cooling mode. Because the air outside the home is cooler than the hot compressed gas refrigerant in the coil, heat is transferred from the refrigerant to the outside air. During this process, the refrigerant condenses back to a liquid state as it cools. The warm liquid refrigerant is pumped through the system to the expansion valve at the indoor units.
STEP 4
The expansion valve reduces the pressure of the warm liquid refrigerant, which cools it significantly. At this point, the refrigerant is in a cool, liquid state and ready to be pumped back to the evaporator coil in the indoor unit to begin the cycle again.
A heat pump in heating mode operates just like cooling mode, except that the flow of refrigerant is reversed by the aptly named reversing valve. The flow reversal means that the heating source becomes the outside air (even when outdoor temperatures are low) and the heat energy is released inside the home. The outside coil now has the function of an evaporator, and the indoor coil now has the role of the condenser.
The physics of the process are the same of how a heat pump works in cooling mode. Heat energy is absorbed in the outdoor unit by cool liquid refrigerant, turning it into cold gas. Pressure is then applied to the cold gas, turning it to hot gas. The hot gas is cooled in the indoor unit by passing air, heating the air and condensing the gas to warm liquid. The warm liquid is relieved of pressure as it enters the outdoor unit, turning it to cool liquid and renewing the cycle.
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