Frequently Asked Questions
An air source heat pump (ASHP) is an energy-efficient alternative to a furnace and air conditioner, even in colder climates and in those with moderate cooling needs. It is an attractive option because it is capable of providing efficient cooling, along with heating in the spring and fall, with a single piece of equipment.
ASHPs use electricity to transfer energy between indoor and outdoor air. Because they move heat, these systems typically consume less electricity than electric-resistance heating systems. In the cooling mode, the heat pump functions like an air conditioner, moving heat from inside to outside the home. In the heating mode, the refrigerant flow is reversed to extract low-temperature heat from outdoors and deliver concentrated high-temperature heat to the home.
There are two types of heat pumps:
- Furnace integrated system: An ASHP with an electric furnace or fossil fuel heating system. These units are installed in homes with forced air systems (ducts) and with existing electric or non-electric heat.
- Mini-split ductless system: This system has an outdoor condenser, just like any heat pump or central air conditioner, but inside the home it consists of one or more indoor air handling units mounted on interior wall space in key locations throughout the home. The mini-split is used in homes that do not have ductwork. Typically, these are homes use electric baseboard, slab, or hydronic (boiler) heating. This system enables you to have a central air conditioning system and high efficiency heating without having a forced air, ducted system.
ASHP systems typically work well in temperatures as low as 30°F. Below this temperature, an additional heating source is required. The backup system can be electric, fossil fuel, or a combination.
Yes, for homes that do not have a forced air or ducted distribution system, the mini-split ductless system will provide the heating and cooling from one system. This system is very efficient because it works in conjunction with your existing heating system—baseboard, boiler, or slab heating—to optimize the efficiency of the whole system. It consists of individual air handling units (wall units) placed in strategic locations throughout the home.
The ASHP is an integrated unit that provides high efficient cooling along with efficient heating in the spring and fall and is capable of interfacing with your existing heating system. Because it is a refrigeration system that provides cooling and then reverses itself to provide heating, it does have a defrost cycle. The ASHP is installed with controls that automatically provide supplemental heating during the defrost cycle and when the temperature gets below the balance point of 30–35°F. The controls also prevent the backup system from coming on when it is not needed.
Although an ASHP is very similar to a central air conditioner with heating, it is important that your installer explains how to operate the system to maximize energy efficiency. How you operate any heating and cooling system has a significant impact on your energy costs. Two families living in identical houses can have different utility costs, with one family paying 50% less, based on proper operation of the heating and cooling system. There are a few differences between a heat pump system and a typical heating and cooling unit:
- It sounds different than a standard heating system.
- You need to keep snow away from the outdoor condenser. The condenser is actually elevated off the ground.
- It has a defrost cycle, so you will hear the supplemental heating system come on when the unit is being defrosted. During the defrost cycle, you may see steam coming off the outdoor condenser.
- The heat pump may work differently than your traditional furnace if you want to turn down the temperature at night and turn it back up in the morning or at the end of the day. It may take longer to get to the higher temperature you desire. This will depend on the balance point set by the installer and how the controls are set up to bring on supplemental heating.
When properly installed, an ASHP can deliver one and a half to three times more heat energy to a home than electric energy it consumes, so for every unit of energy you put in, you get two to three units in return. As a result, these systems can provide heat for Minnesota’s shoulder seasons (fall and spring) at a higher efficiency and lower cost than electric resistance heating, oil, and propane heating, and in some cases, for a lower cost than gas heating as well.
While ASHPs are gaining popularity in northern climates, they are still a new technology to some Minnesota heating and ventilation contractors. As with any job, it is important to choose an experienced contractor who is trained to install the specific product you have in mind. Ask for references to ensure the quality of the contractor's work and to make sure the contractor meets the program and product training requirements to participate in Minnesota Power's ASHP rebate program. You must use a program participating contractor to qualify for these rebates.
These contractors are trained to properly install a qualifying unit to meet Minnesota Power’s installation requirements. This includes explaining how to operate the ASHP for maximum efficiency, proper sizing, and checking refrigerant charge and air flow on furnace integrated units. According to the U.S. Environmental Agency, recent field research suggests that approximately 75% of installed cooling systems may have incorrect refrigerant charge levels, which can reduce system capacity and efficiency by 20% or more.
Yes, a furnace integrated heat pump can be easily installed to work with your existing forced air furnace. The furnace will be the primary heating system you need during the coldest temperatures. The heat pump will provide efficient cooling in the summer and heating in the spring and fall.
When retrofitting an existing home with an ASHP, it is important to consider the current heating distribution system. If the system uses forced air ducts, a furnace integrated system would be the most efficient. If there are no air ducts in the home, you should select a mini-split ductless system. See the item below for information on qualifying for Minnesota Power’s ASHP rebate program.
Yes, Minnesota Power and participating municipal utilities offer a rebate on qualifying ASHPs. The heat pumps need to meet a minimum Seasonal Energy Efficiency Ratio (SEER—a measure of cooling efficiency) and Heating Seasonal Performance Factor (HSPF—a measure of heating efficiency) standards. In addition, to qualify for the rebate, electricity must be the primary heating source in your existing or new home. This includes the heat pump with supplemental electric heat. The program participating contractor will work with you to design a system that qualifies for the rebate.
Yes, ASHPs meet the requirement for electric heat (as described above) for the Triple E New Construction program. For more information on this program, click here.
When planning a new home, work with your builder, heating and cooling contractor, and local utility to determine the type of heat pump that complements your energy-efficient design. Heat pumps offer an energy-efficient option that enhances the overall energy savings in your new home.
Minnesota Power also offers a rebate on Ground Source Heat Pumps (GSHPs). GSHPs are similar to ASHPs, but they use ground temperature (rather than air) via buried piping or drilled wells and can provide 100% of the buildings heating and cooling needs.
Talk with you installer to determine how frequently your system needs to be tuned up. It is a high efficiency heating and cooling system so it should be looked at periodically to maintain optimum efficiency and operation.