How to compare air source heat pump options
Last updated 9/27/2019
Your air source heat pump system design will be customized to your property. The solution that’s best for your home or business depends on the existing systems in place, as well as your long-term heating and cooling needs.
Questions to ask when comparing air source heat pump options
Air source heat pump systems can take many different forms. You’ll need to answer the following questions before you can make a final decision about your installation:
- Will you use air source heat pumps as your sole heating source?
- Do you want a system with or without ducts?
- Are you looking to heat an entire building, or a single room?
- Do you want a split or packaged system?
- Will a traditional system be sufficient for your needs, or should you look into a cold-climate system?
You can use air source heat pumps as the only source of heat in your building, but if you have an existing system, you may want to keep it.
If you power your air source heat pumps with renewable electricity (such as a solar panel system), you can theoretically eliminate your use of fossil fuels entirely and have a net zero home. However, relying on air source heat pumps as your sole source of heat in colder climates can be trickier because certain heat pump technologies don't operate as efficiently in sub-zero temperatures. There are many heat pumps designed specifically for colder climates (i.e. cold-climate models with high HSPF ratings), but some standard heat pumps will only operate efficiently above 25 to 30 degrees fahrenheit.
If you want to use air source heat pumps as your sole heat source, it’s important to ensure that your home is well-insulated and as energy efficient as possible. This is easiest if you’re building a new home, because you can prioritize energy efficiency measures during construction.
However, in most cases homeowners choose to retrofit their home with air source heat pumps, keeping their existing heating system in place as a backup on colder days. This is particularly true in colder climates, or for homeowners who have built a new addition to their home that doesn’t have an existing heating supply. As an added benefit, if you’re installing heat pumps as a retrofit, you can often make use of existing ductwork.
Air source heat pumps can distribute air throughout your building with the use of ducts (a “ducted” system) or via individual wall-mounted units (a “ductless” system, also known as a “mini-split”).
Both ducted and ductless systems require an exterior unit on the outside of the home, and both can be used to heat and cool your building. The biggest difference between the two is that a ducted system will make use of ductwork inside the walls of your home, while a ductless system would not. In a ducted system, the outdoor unit is connected to an indoor air handler that will fan the warm or cool air through your ducts and around your building. The air will come out through the vents your ducts are connected to. Ductless systems, on the other hand, have individual indoor units placed inside a room at a given zone. These units, often referred to as “heads,” are connected directly to the outdoor unit(s) through refrigerant piping lines that transfer the warm or cool air, and push warm or cool air into the room.
Homeowners who are concerned with having a visually obtrusive system tend to choose a ducted system that connects the air source heat pump to their existing ventilation system, as they would prefer not to have the heads visible in their living space. This is becoming less of an issue as heat pump manufacturers develop newer low-profile heads.
If you want a ducted system and already have ductwork in your home from an existing heating and cooling system, your air source heat pumps can be retrofitted to use your existing ductwork. In some cases, you’ll need to make upgrades to your ductwork or electrical system during the installation process to ensure that it efficiently distributes air.
If you don’t have existing ductwork, installing a ducted system will take longer and cost more than a ductless system, because you’ll need to install ductwork within the walls of your home or business. In these cases, ductless systems have fewer construction requirements, and tend to be less expensive than ducted systems.
Another option that’s a bit of a hybrid between the two is a short-run, or mini-ducted system. Ductwork is involved in this type of installation, but the ductwork only runs through specific portions of the house rather than a central ducted system. Then, you can install ductless units anywhere in your building that isn’t heated and cooled through the existing ductwork.
A single zone air source heat pump system is meant to heat only a small amount of space, typically one room. Single zone systems have an outdoor unit that connects to one indoor head to deliver heat or cool the area.
Single zone systems are the way to go if you’re looking to only heat or cool a small area of your home. A common use of a single zone system is to heat or cool a newly constructed addition to your home, when the rest of the house is run on a central air conditioning system. You can choose to install multiple single-zone systems, but if you’re looking to heat or cool many rooms using air source heat pumps it will be more efficient to install a multi-zone system.
A multi-zone system can heat and cool multiple sections of a home with the use of multiple heads in different areas, all connected to a single outdoor condenser. If you install a multi-zone system, you can heat or cool various “zones” within your property at different temperatures at the same time. For example, during hot summer months you can set the temperature of the room where you spend the most time to a lower temperature, while other zones are set at a higher temperature to reduce your overall energy use.
The majority of systems today are split, which means they have two coils: one inside, and one outside. The coils of an air source heat pump system are the component that actually heats or cools the air. Split systems exist with both ducted and ductless systems.
By comparison, in a packaged heat pump system, coils and fans are located at the outside unit, and heated or cooled air is distributed throughout the building via ductwork. Packaged systems tend to be less efficient than split systems, but the installation is less labor intensive (and therefore less expensive) than split systems. Packaged systems also take up less overall space, and may be worth considering if you have a home with limited available space.
Cold-climate air source heat pumps are a newer technology than a traditional air source heat pump, and are designed to be more efficient for heating homes in colder regions like New England or the Midwest. Cold-climate air source heat pumps can either be ducted or ductless, single-zone or multi zone, but in order to be considered a “cold-climate” system they need to meet certain efficiency criteria. Air source heat pumps that are more efficient are typically more expensive upfront.
How to evaluate different air source heat pump technologies
Once you’ve decided what type of air source heat pump installation you’re moving forward with, you have to select the equipment you’ll use. There are three ratings & certifications to help you make your decision:
- SEER rates how efficiently an air source heat pump cools a space.
- HSPF rates how efficiently an air source heat pump operates in heating mode.
- ENERGY STAR is a government rating awarded to high efficiency appliances that meet specific standards.
The Seasonal Energy Efficiency Rating (or SEER) rates a system’s cooling efficiency, making a high SEER rating especially important in warmer climates. Federal regulations require a minimum of 13 SEER for homes in the Pacific Northwest, Northeast, Midwest, and Mountain states. For homes in warmer areas of the country, the SEER requirement is raised to 14. Generally speaking, the higher the SEER, the more expensive the system is, but if you live in an especially warm climate it may be worth paying for a system that’s more efficient for your own comfort.
The Heating Seasonal Performance Factor (HSPF) rates a system’s heating efficiency, making it is the cold-climate equivalent of SEER. If your property is located in a colder climate you should be shopping for a system with a higher HSPF. A HSPF rating of 7.7 is required under federal law for all air source heat pumps.
ENERGY STAR Label
Air source heat pumps with an ENERGY STAR label are certified by the Department of Energy as having above-average efficiency, making them the best choice for saving energy (and, therefore, saving on your utility bills). Air source heat pumps with the ENERGY STAR level are going to have high SEER and HSPF ratings. To receive an ENERGY STAR label, an air source heat pump must have a SEER above 15 and a HSPF above 8.2 for single packaged systems, and 8.5 for split systems.