Air-Source Heat Pumps
Air-source heat pumps (ASHPs) are a type of heat pump that exchange heat between a building and the outside air by circulating refrigerant between indoor and outdoor components, similar to a central air conditioner’s outdoor condenser and indoor evaporator.
Unlike a central air conditioner, ASHPs can reverse their refrigeration cycles to provide heating, too. In recent years, “cold-climate” ASHP technology has advanced so that many models can provide space heating without fossil fuel backup at very low outdoor temperatures. Sometimes ASHPs are referred to as cold-climate heat pumps, or "CCHPs."
If you have questions about GSHPs and our available rebates, please call us at (802) 865-7336.
- ASHPs can provide an easy-to-install heating and cooling solution for buildings without ductwork and can provide a spot comfort solution for rooms that were not previously conditioned.
- ASHPs can be more affordable than other heat pump system types, so can serve as a more accessible way for some building owners to strategically electrify and reduce their carbon footprint.
- For cooling, an ASHP may cost 40% less to operate than room air conditioners of equivalent capacity.
- For very well-insulated and air-sealed buildings, ASHPs do not require a fossil fuel backup for operation in extremely cold outdoor temperatures.
- ASHP equipment can last 12 – 15 years, depending on the installation location and exposure of the outdoor unit. Refer to manufacturer’s manuals for specific preventative maintenance tasks for equipment.
NOTE: If you heat your building with natural gas - as most Burlingtonians do - you might not save money with an air-source heat pump; your electric bill could go up by more than your gas bill goes down. If you are considering an air-source heat pump, consider a ground-source heat pump instead, and also think about weatherizing first.
Use the calculator below to get your own simple economic analysis of an ASHP and your existing heating system using Burlington energy rates.
Contact the BED Energy Services team to get started with free, unbiased advice. We’ll walk you through the decision-making process and help you maximize your energy investments.
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Ductless “Mini-Split” Systems
Ductless, mini-split heat pumps are a common type of ASHP serving Burlington homes and businesses.
How They Work
Mini split heat pump systems pump refrigerant between an outdoor unit and an indoor unit (or multiple indoor units). As the name implies, these systems do not include ductwork for distribution; indoor units recirculate room air using the onboard fan.
Indoor units are sometimes called evaporator units and outdoor units are sometimes called condenser units, but since heat pumps can reverse their refrigeration cycle to operate in either heating and cooling mode, it is more accurate to keep it simple and call them ‘indoor’ and ‘outdoor’ units.
In cooling mode, the indoor unit serves as the evaporator and the fan blows air over cold coils to remove heat from indoor air using refrigerant. The outdoor unit serves as the condenser, and hot coils reject heat from the indoor spaces via the refrigerant loop into the outside air.
In heating mode, the heat pump flips its operation, and the indoor unit serves as the condenser and the fan blows air over hot coils to add heat to indoor air using refrigerant. The outdoor unit serves as the evaporator, and cold coils reject heat from the indoor spaces via the refrigerant loop into the outside air.
A fossil fuel source is usually maintained as a backup heat source to avoid heat pump operation during extremely cold outdoor conditions, when the equipment relies on electric resistance elements instead of the refrigerant loop to provide heat to indoor spaces.
- How well an ASHP heats and cools your home depends on the number of inside wall units, the floor plan, and the insulation and air-sealing quality of the building. Field studies show that ASHPs work best in weatherized buildings. In some buildings it is more cost-effective to weatherize along with the ASHP installation or weatherize first and install heat pumps later.
- Typically, ASHPs cannot serve as a full replacement of an existing heating system as they don’t condition every room in a building and may be unable to provide enough heat during extremely cold outdoor temperatures.
- A single outdoor unit can serve up to four indoor units, and a single indoor unit can condition multiple rooms; these are called ‘multi-zone’ or ‘multi-head’ installations.
- A building may be served by multiple outdoor and indoor units depending on the number and size of the spaces needing conditioning.
- Consider locating indoor units less than 50 feet away from outdoor units to improve comfort and energy performance.
- Variable refrigerant flow (VRF) designs offer enhanced comfort and energy savings by pumping refrigerant to match demand for both heating and cooling simultaneously from a group of indoor units which can result in increased energy savings.
- BED can offer custom rebates for VRF systems serving commercial buildings. Call us at 865-7440 or write us to discuss potential energy savings and financial rebates.
- Indoor units are usually hung on walls but can also be suspended from ceilings and mounted flush with drop ceilings.
- Outdoor units are usually installed on curbs 4 to 8 inches above the ground, but can also be installed on flat roofs.
- Avoid placing units near gutters as water may drip on unit in winter and freeze, restricting air flow through the unit and reducing its efficiency.
- Refrigerant piping must be routed through walls and ceilings between outdoor and indoor units and should be insulated per Vermont’s residential and commercial building energy standards, as applicable.
Centrally Ducted Air-Source Heat Pumps
Ducted ASHP systems use existing ductwork in a building to distribute conditioned air for both heating and cooling.
Heat pumps can be retrofit to work with your existing furnace. Customers considering these ASHP systems should work with HVAC contractors with controls systems experience to program a centrally ducted ASHP system for effective and energy-efficient operation.
Air-to-Water Heat Pumps
Air-to-water heat pumps integrate with hydronic distribution systems to circulate water for heating and cooling, and can provide domestic hot water. Hydronic distribution uses water as a heat transfer fluid to distribute heat.
Heat pumps can be retrofit to work with your existing boiler. Customers considering these ASHP systems should work with HVAC contractors with controls systems experience to program an air-to-water ASHP system for effective and energy-efficient operation.
If you are heating with anything other than natural gas, BED offers $375 or $450 toward the purchase of an eligible ductless mini-split system (CCHP). You may also be eligible for rebates on weatherization.
Vermont Gas Customers: Rebates for qualifying cold-climate ductless mini-split, centrally ducted, and air-to-water ASHPs are available for all BED customers. Burlington Electric Department has contracted with Efficiency Vermont to administer these rebates; income-eligible customers may qualify for bonus rebates:
- Rebates for ductless mini-split ASHP systems
- Rebates for centrally ducted ASHP systems
- Rebates for air-to-water ASHP systems
Before making a purchase, review the current list of qualifying equipment. Qualifying models satisfy ENERGY STAR requirements for energy and cold climate performance. Call the BED Energy Services team at 865-7336 with your project-specific questions.
- Ductless mini-split ASHP qualified products list
- Centrally ducted ASHP qualified products list
- Air-to-water ASHP qualified products list
Energy Savings Calculator
Check out potential savings yourself using our basic energy savings calculator to assess if an ASHP system would be cost-effective for your building.
Actual savings can vary considerably for any customer depending on a wide number of variables including:
- Current costs per gallon of propane or oil.
- Extent of building weatherization. All types of heat pumps perform better in tighter and well insulated buildings.
- The type of fuel you'd be replacing:
- ASHP systems provides good savings over propane gas at current prices and when looking at the past five-year average.
- ASHP systems provides little to no savings over oil at current prices but shows stronger savings when looking at the past five-year average.
- ASHP systems provide no savings over natural gas at current prices and when looking at historical prices.
- The combustion efficiency of your current heating system (a range of about 65 to 95%).
- Amount of displacement of the existing space heating load by the new ASHP system depends on the number of wall units installed, layout of the home, and how the ASHP system is used.
- The severity of the heating season compared to other years (average temperatures can vary about 5 to 20% between years).
- Whether the ASHP system displaces a less efficient air conditioning (AC) system, which may result in cooling savings.
- Whether ASHP provides AC where none was present, thereby increasing costs.
For Commercial Heat Pumps (5 – 20 tons), try this Energy Costs & Savings Calculator.
|Space heating fuel|
|Water heating fuel|
|Total annual fuel consumption|
|Current est. space heating cost|
|BED Incentive||($ )|
|How much of your existing heating system will be displaced by your new CCHP?|
|New estimated space heating cost|
|Estimated CCHP simple payback|