Ductless heat pumps, or mini split heat pumps, are an alternative to radiator or baseboard heating, as well as a replacement for window units for cooling. No duct work is needed. Instead, a head unit, or multiple head units, are mounted on an interior wall or ceiling, with an accompanying unit outside. The outside unit extracts heat from the air, even when it’s cold. Refrigerant carries the heat directly to the head(s) inside, which then delivers heated air to occupied space. In warmer months, the system works in reverse for quiet, efficient air conditioning. The illustration demonstrates how a ductless heat pump works in both cold and warm seasons, doing double duty to keep your home comfortable no matter the temperature outside.
Mini Split vs. Ducted Systems
Mini split heat pumps, or ductless heat pumps, are specifically designed for homes or sections of homes that do not have ductwork. If your home does have existing ductwork, a ducted ASHP system may be the right system for you. Ducted ASHP systems can be installed and connected to the conventional forced-air ductwork system that is typical of most American homes. To learn more about ducted ASHP systems, visit www.energystar.gov/products/air_source_heat_pumps.
Additional Benefits of Mini Splits:
- Lower energy bills by switching from electric resistance, propane, and oil to heat pumps.
- No combustion means better indoor air quality because there are no direct emissions such as NOx, carbon dioxide, or carbon monoxide.
- No fuel storage or risk of running out of fuel.
Is a mini split right for you?
Mini splits can be utilized for whole home heating and cooling, but are also a great fit to supplement your existing HVAC system depending on your needs.
Mini splits are increasingly being used in situations, such as:
- Homes with costly electric heat (e.g., baseboard, furnace, wall heaters, electric radiant) that will also benefit from cooling.
- Older homes with no existing ductwork (e.g., radiators or baseboard heat) that have never had central air conditioning before.
- Existing homes with high fuel costs.
- Additions or outbuildings (e.g., shed, barn, garage) where extending ductwork or heating/cooling capacity is difficult. Spaces adjacent to unconditioned spaces where ductwork would be exposed to harsher temperatures (e.g., a guest room above a garage).
- New, high-efficiency homes, including ENERGY STAR certified homes.
- Older commercial buildings with no existing ductwork for air conditioning or expansions.
- Where hot or cold spots exist within homes including spaces which serve as home offices.
- Rooms require additional heating with a preference to reduce fossil fuel consumption from primary heating source.
- Buildings with an older central heating unit that would like to replace it with a whole home clean heating solution.
Installing properly sized HVAC equipment for your home is essential to getting the best performance and comfort. A system that is either too large or too small for its intended space will struggle to meet your home comfort needs. Your HVAC contractor can help determine what sized system is right for your home. Your contractor should verify the proper size system for your home using a tool called "Manual J" - a calculation of the amount of heating and cooling your home requires to keep you warm in the winter and cool in the summer.
Cold Climate Considerations
Many new ENERGY STAR certified mini split models excel at providing space heating even in the coldest of climates, as they use advanced compressors and refrigerants that allow for improved low temperature performance. If you live in a climate where winter temperatures regularly dip below freezing, talk to your contractor to choose an ENERGY STAR certified unit suited to your particular home. When you ask your contractor for an ENERGY STAR certified cold climate ASHP, you can be confident that your new AHSP system will deliver the heating performance and efficiency benefits you expect on even the coldest winter days. A good contractor will work with you to determine the size and potential integration with a back-up heating system that will work best for your home.
Climate ASHP technology has improved significantly over the past several years, and many ASHP systems are capable of delivering heating capacity and efficiency at low outdoor temperatures. The ENERGY STAR certification requires third-party verified performance for low temperatures, testing ASHPs down to 5°F. Testing cold climate ASHP performance at 5°F ensures that your ASHP will provide all the heat you need to keep your home comfortable all winter. Your cold climate ASHP will continue working at temperatures below 5°F, but pairing it with a back-up energy source will heat your home the most efficiently when temperatures are even lower.
Take Advantage of Incentives
Air source heat pumps that earn the ENERGY STAR are eligible for a federal tax credit up to $2,000. This tax credit is effective for products purchased and installed between January 1, 2023, and December 31, 2032. Learn more at www.energystar.gov/taxcredits. Many utilities also offer incentives for installing ENERGY STAR certified ASHPs. Check with your local utility for more details or go to: www.energystar.gov/rebatefinder.
What else should I look for when buying a mini split?
Remember, even though these products can be more expensive to purchase up front, the cost difference will be paid back over time through lower energy bills. Consider regular maintenance of your heating and cooling system to prevent future problems and unwanted costs. Mini splits are one of six high-impact improvements to your home that work together to deliver significant energy and cost savings. Learn more about additional improvements with the ENERGY STAR Home Upgrade.
Finding Certified Equipment
Be sure to look for the ENERGY STAR when shopping for a ductless heating and cooling system
Air-source heat pumps. Use the ENERGY STAR Product Finder to help you identify high efficiency equipment that meets the latest ENERGY STAR certification criteria and then work with a professional installer to find the model that is right for you. Be sure to shop around for a well–reputed contractor familiar with “ductless” or “mini–split” systems. ENERGY STAR offers tips on how to hire a contractor.
- Remember that heat rises and cool air sinks, when gauging expectations for what areas of your home will receive benefits from a single wall unit.
- Consider air flow. Open spaces are generally easier to cool and it can be challenging for heat to move through an open doorway, and impossible to move through a closed one.
- Simplify your installation process through creative placement. By running wiring (line set) through closets, basement/attic stairways, attached garages, basements, crawlspaces, or attics, you can minimize the need to patch or paint walls and ceilings, and benefit from the aesthetics of minimal wiring.
- Plan for an outdoor location that will be least intrusive based on your home and outdoor living needs. The right location will come at the intersection of personal aesthetic preference and home layout.
- Prioritize unobstructed airflow by avoiding tight placements with shrubs, structures, etc. The more air they have access to, the better they'll work.
- Avoid installing the outdoor unit near doors and windows. Outdoor units release water when they defrost in the winter, which can form icy patches.
- Check the location related to roof runoff, and make sure the unit is equipped with a rain cap if necessary.
- Consider serviceability and ease of access when selecting an installation location.
Utilize all year long – Your heat pump is more energy-efficient than a furnace or boiler, even during winter. If you have both, you should use your heat pump year-round.
Stick with a steady temperature – Unlike a furnace or boiler, heat pumps do not save energy by turning it down when you’re away or asleep. For best use, pick a comfortable temperature and leave it there.
Avoid Auto mode – Make sure your heat pump is set to “heat” or “cool” to avoid the system switching modes during unseasonably warm or cold days.
Optimize fan speed – Utilize the “auto fan” setting or adjust the fan to the lowest speed that will spread the heated or cooled air far enough to meet your needs.
Clean your dust filters – Just like traditional HVAC systems, heat pumps work best with clean filters. Heat pump filters should be cleaned when visibly dirty or when indicated by the filter light.