Heat pumps are a magical technology rich in benefits: Compared to traditional heating and cooling systems, they boast high efficiency, lower energy bills, and climate compatibility. Heat pumps rely on electricity — not fossil fuels — to heat and cool spaces, offering year-round comfort within a single system.
Maybe it’s because of all that the heat pump has to offer, along with some confusing terminology (despite its name, a heat pump also cools) that its capabilities seem tough to conceptualize. If you’ve been trying to parse out the difference between a mini-split and a ducted heat pump system, or you’re trying to better understand efficiency labels, this guide is for you.
Our hope is that this here ”official“ heat pump glossary can help you sift through the jargon and get to the heart of what matters with this supreme innovation. And then, the future is yours.
Air source heat pump (ASHP)
An air source heat pump heats and cools a space by transferring heat between the indoor and outdoor air. There are two main types:
- Air-to-air heat pumps
Air-to-air heat pumps are air source heat pumps (see above). Powered by electricity, they have the ability to both heat and cool a space, and are known for their energy efficiency and positive environmental impact,
- Air-to-water heat pumps
This type of heat pump transfers heat from the outside air to water, which then can be circulated through radiators, underfloor heating systems, or water storage tanks. While these devices are primarily used for heating, they can also cool: The cooled down water can absorb heat from inside, thus cooling the space. Some users rely on air-to-water heat pumps for hot water, which can eliminate the need for a second water heater.
Air-handling units, air handlers, or heads
(Also see: mini-split, ductless)
An air handler is the device that contains the fan and indoor heat exchanger; it circulates the air inside a home. (At Quilt, our air handlers are called indoor units — we like to be direct). The design and function of air handlers will vary depending on the type of HVAC system it is associated with. The air handler is the device affixed inside the room that’s controlled by a thermostat or remote. Ductless systems usually have multiple heads that can be individually controlled.
BTUs
BTU is the acronym used for British Thermal Units. One BTU is a unit of measurement that quantifies the amount of energy (or heat) required to raise the temperature of one pound of water by one degree Fahrenheit. In the context of HVAC systems, BTUs measure the energy output of a system per hour, be it a heat pump, air conditioner, or furnace. This is designated as BTU/h.
In heating, the higher the BTU/h rating, the more heat the system can generate. Systems with a higher BTU/h mean a system can produce more heat to warm larger spaces. Conversely, for cooling, BTU/h measure the system’s ability to remove heat from the air, which cools a space. Systems with higher BTU/h ratings can cool larger spaces.
CEE tiers
CEE stands for Consortium for Energy Efficiency, which is an organization that sets voluntary efficiency performance levels for various systems and appliances. CEE tiers, of which there are three, are meant to help consumers understand the efficiencies of different products.
- Tier 1: These products meet or slightly exceed the basic energy efficiency standards designed for that product.
- Tier 2: These products have greater efficiency than tier 1. Products must meet tier 2 efficiency guidelines in order to qualify for IRA rebates.
- CEE Advanced Tier (sometimes called Tier 3): These products boast the highest level of energy efficiency recognized by the CEE — they tend to be the most expensive, but also the most cost-effective in the long run because of their energy savings. Systems that meet this tier require demand response to be integrated into its capabilities.
Equipment with CEE Tiers 2 and 3 generally reduce energy consumption and greenhouse gas emissions; higher tiers are also more likely to align with the requirements to qualify for rebates and incentives from utility companies.
When it comes to HVAC systems, including heat pumps, furnaces, and air conditioners, CEE tiers are designed on a handful of efficiency metrics. These include SEER2 for heat pumps and air conditioners, HSPF2 for heat pumps.
Central heat pump
A central heat pump is a heating and cooling system powered by electricity; it can replace a furnace and air conditioning system all in one. The “central” part of central heat pumps refers to ducts: Central heat pumps distribute conditioned air by a ducted network configured in the home.
Circuit breaker
A circuit breaker is an electrical switch that protects an electrical circuit from damage, helping to prevent fires and destruction to wiring and appliances. Its function is to automatically cut off the flow of electricity when it detects an excessive current flow.
Compressor
The compressor, located within the outdoor unit, is a device responsible for driving refrigerant flow throughout a heat pump system.The compressor takes in refrigerant as a low-pressure, low temperature gas and outputs refrigerant as a high-pressure, high temperature gas. This pressure and temperature difference allows heat to be absorbed on one side of the system and removed on the other side of the system.
Condensation line
A heat pump’s condensation line — also referred to as a drain line or condensate drain line — is a pipe that helps remove moisture from the indoor unit, which is produced during the cooling process. Condensation occurs in the cooling process as warm, humid air passes over the evaporator coil. This water drips into a pan beneath the coil, and is then drains outside the house (or into a designated drainage system) through the condensation line.
COP
COP, which stands for Coefficient of Performance, measures the efficiency of a heat pump: It signifies how much heating or cooling a heat pump provides for each unit of electricity it consumes.
Heating COP measures how efficiently the heat pump can extract heat from outside to warm the inside. Cooling COP measures how efficiently the heat pump can extract heat from inside to cool the area.
When operating at their rated conditions, heat pumps typically have a COP range from 3 to 5, where the higher the COP, the more efficient the system. A heat pump with a COP of 5, for example, can provide 5 times the energy that it consumes. A higher COP equates to lower energy costs and increased environmental benefits, since the system is more efficient in converting electrical energy into heating or cooling.
Cold climate air-source heat pumps
These types of heat pumps are specifically designed to perform in temperatures that dip below 5°F. Along with other features, the systems are equipped with automatic defrost cycles to prevent ice build-up on the outdoor unit. To be designated for cold climates, a heat pump must meet certain criteria outlined by Energy Star, including a COP of at least 1.75 when temperatures are 5° F. Quilt's system is a cold climate heat pump.
Ducted
(Also see: central heat pump)
Ducted systems use a network of ducts to distribute air throughout a home. Central HVAC systems, as well as central heat pumps, are anchored by a single system and rely on ducts to move the same heated or cooled air throughout multiple rooms or an entire home.
Ductless
(Also see: air handlers, mini-splits)
Ductless systems — also called mini-splits — rely on independent indoor units to distribute conditioned air in individual rooms or zones. Every mini-split has its own control (whether that’s a remote or a thermostat), which allows for each room or zone to be set at its own specific temperature.
Ductless systems can have multiple indoor units connected to the same outdoor unit; different systems offer different ratios of indoor units to outdoor units. (The Quilt system, for example, connects up to two indoor units for every outdoor unit.) There are certain trade offs when it comes to having fewer or more zones connected to one outdoor unit. Having fewer indoor units per outdoor unit is typically more efficient and allows the user to have more control over each zone. Having more indoor units connected to one outdoor unit reduces the number of outdoor units necessary and, in some cases, may help reduce costs.
Geothermal or ground source heat pump (GSHP)
This type of heat pump is an efficient system that relies on the heat of the earth to transfer heat (unlike air-source heat pumps, which rely on the heat of the air). Like the air source heat pump, GSHPs can heat and cool. In heating mode, geothermal heat pumps extract heat from the ground and transfer it inside the home. In cooling mode, they remove heat from the home and transfer it to the ground.
HSPF2
HSPF2, which stands for Heating Seasonal Performance Factor 2, measures the amount of heating provided by a heat pump across a range of typical heating conditions for the amount of electricity it consumes. The higher the HSPF2 rating, the more efficient the unit — which means lower operating costs and energy use. In order to qualify for Energy Star and available tax credits, systems must meet or exceed an HSPF2 of 9.5. The best, most efficient 2-zone systems on the market have an HSPF2 between 8 and 11. Quilt’s HSPF2 is 12.
Heat exchanger
A heat exchanger is a device used in a heat pump to transfer heat between the refrigerant and the air (or water) that’s being heated or cooled.
A ductless mini split heat pump system typically has one heat exchanger in its outdoor unit and one in the indoor unit. In the outdoor unit, the device absorbs heat from the air outside when in heating mode. When in cooling mode, it releases heat to the outdoors.
The indoor heat exchanger (which can also go by evaporator or condenser) transfers heat between the indoor air and the refrigerant. When heating, the heat exchanger releases heat to the indoor environment. When cooling, the heat exchanger absorbs heat from the indoor air.
HVAC
HVAC is an acronym that stands for Heating, Ventilation, and Air Conditioning. HVAC systems can control the temperature, humidity, air quality, and circulation of indoor air, usually with the goal of providing comfort or ideal conditions for whatever may be inside.
Hybrid heat pumps
A hybrid heat pump — also called a dual-fuel heat pump — combines the technology of a traditional heat pump with a secondary heating source, typically one that runs on fossil fuels like gas, propane, or oil.
Line hide
A line hide is a protective cover or casing that conceals the refrigerant lines and wiring that run between a heat pump’s indoor and outdoor units. They’re commonly used with ductless mini-splits. Line hides can be painted and designed to blend in well with a home, which can help with curb appeal. Beyond the aesthetic add of line hides, they help protect the refrigerant lines and electrical wiring from weather-related damage, along with other physical threats, like nosy animals or accidental punctures from lawn equipment or other activities.
Mini-split
(Also see: air handler, ductless)
A mini-split system refers to the entire ductless heat pump system, which includes the indoor and outdoor units, the refrigerant lines, and the line hides. Mini-split is sometimes colloquially used to describe the indoor unit — the air handler or head that gets mounted on a wall, ceiling, or floor that can heat or cool individual rooms or zones.
R32
R32 — also known as difluoromethane — is a type of refrigerant commonly used in HVAC systems. This HFC (hydrofluorocarbon) refrigerant has a lower Global Warming Potential (GWP) compared to older iterations, including the popular R410A. It is considered more energy-efficient than many other refrigerants, and has a higher heat transfer efficiency, which allows HVAC systems to operate better.
Refrigerant
Refrigerant is the working fluid used in heating and cooling systems. It can be compressed to high pressures and temperatures to reject heat to indoor or outdoor environments, and also expanded to low pressures and temperatures to absorb heat from indoor or outdoor environments.
Refrigerant lines
Refrigerant lines are a set of insulated pipes that carry the refrigerant between the indoor and outdoor units of a heat pump system.
SEER2
SEER2, which stands for Seasonal Energy Efficiency Ratio 2, measures the amount of cooling provided by a heat pump across a range of typical cooling conditions for the amount of electricity it consumes. The higher the SEER2 rating, the more efficient the unit — which means lower operating costs and energy use. To qualify for Energy Star and available tax credits, systems must meet or exceed a SEER2 of 16.
Standard heat pumps typically fall between 13 and 15, high-efficiency models range from 16 to 19, and the most advanced systems achieve SEER2 ratings of 17 to 24. Quilt’s SEER2 is 25.
Tons
A ton is a unit of measurement that refers to the cooling or heating capacity of an HVAC system. One ton is equivalent to the ability to transfer 12,000 BTUs of heat per hour.