Heat pumps are a popular choice for central air in the South. They both heat and cool—despite the somewhat misleading name—and can help save money on utilities. If you’re wondering what a heat pump is, these efficient HVAC systems operate a little differently than traditional furnaces and work best in mild climates. We’ll tell you how heat pumps work, what kinds of heat pumps are out there, and what to consider when deciding if a heat pump is right for your home.
How Heat Pumps Work
Unlike a traditional furnace, heat pumps don’t generate any heat. A heat pump is a single system that can both heat and cool by absorbing and transferring heat. In winter, heat pumps extract heat from the outdoors (or underground) and pump it inside. In summer, your heat pump will do the opposite and release heat from your home to the outdoors, much like a traditional air conditioner.
Types Of Heat Pumps
There are two major kinds of heat pumps: air-source heat pumps and geothermal heat pumps. Air-source heat pumps are much more common because of the ease and cost of installation. Geothermal heat pumps work by pushing heat underground or pulling it from underground, depending on the season.
Air-Source Heat Pumps
These look much like a traditional heating and cooling system, with an outdoor unit, an indoor air handler, and ductwork. Because you are only purchasing one system, air-source heat pumps are generally less expensive than buying a separate furnace and air conditioner. They come in a range of sizes and levels of energy-efficiency. Most air-source heat pumps do best in a mild climate with winter temperatures that rarely drop below freezing.
Geothermal (Ground-Source) Heat Pumps
Geothermal heat pumps are incredibly efficient because of the consistency of underground temperatures. Fluid-filled pipes and an indoor air handler work to transfer heat from or to underground.
Geothermal heat pumps are expensive to install because of the extensive piping required. An installer may drill a deep well under your home (at least 100 feet down) for a vertical system, or run looping pipes through a long trench on larger properties. Though installation is a big project, geothermal heat pumps have advantages: They will work in the coldest climates and can save 25-50 percent on energy bills.
Components Of A Heat-Pump System
Both types of heat pumps use an indoor air handler with refrigerant-filled coils, a compressor, and fan to blow air through ductwork. The heat pump compressor moves refrigerant through the coils to capture or release heat. The fan blows air across the coils to warm up air or cool it, depending on the season.
An air-source heat pump also has an outdoor unit, so that the two units can work in tandem to heat or cool the air inside your home. Both types have a reversing valve to change the flow of refrigerant, sending warm fluid indoors when you need to heat your home or outdoors when you need to cool it. An expansion valve controls the pressure and temperature of refrigerant in the coils.
Some air-source heat pumps have an emergency heating system that kicks in when temperatures drop below freezing. These systems use electricity to produce heat and can become expensive to run in cold climates.
Heating And Cooling Modes
How Heat Pumps Cool In Summer
Now we’ll get technical and dive into the details of how each mode works on a heat pump. In summer, the indoor unit acts as an evaporator, blowing warm air from your home across the coils. Refrigerant in the coils captures the heat, cooling the air to then send through your ductwork.
The compressor pressurizes the refrigerant into hot gas, which is sent to the coils in the outdoor unit or underground. The refrigerant releases the heat outdoors and condenses into liquid as it cools, then returns indoors to repeat the cycle.
How Heat Pumps Heat In Winter
In winter, how does a heat pump capture heat from cold, outdoor air? The refrigerant is still able to absorb enough heat on cold days to turn into a cold gas, which is then pressurized to make it hotter. The system sends the warm refrigerant indoors, where it evaporates heat when air blows across the cools. The air then travels through ducts to warm your home. The refrigerant in the indoor unit cools and condenses, and is sent back outdoors.
Advantages Of Heat Pumps
Because heat pumps merely transfer heat, they are much more efficient than a furnace that runs on propane, oil, or electricity, cutting as much as 75 percent from your heating bills. They run similarly to an air conditioner but do a better job of dehumidifying, which can result in lower energy usage in your home.
Heat pumps don’t always save money if you have a gas furnace, and can result in higher utility bills in a really cold climate. However, heat pumps are more eco-friendly than gas furnaces because of reduced emissions. How much more eco-friendly varies depending on where you live and how much green energy is used in the local electrical grid.
Considerations Before Choosing A Heat Pump
If you live in the South, a heat pump is worth considering when you upgrade your heating and cooling. Here are some things to consider:
- If you’re considering replacing your furnace and air conditioner at the same time, a heat pump could save you money.
- If you live in a mild climate that rarely drops below freezing, a heat pump saves on utility bills. In colder climates, you may want to keep your furnace as a back-up system so you don’t run up your electric bill. You can also buy a dual-fuel or hybrid heat pump that uses both electricity and gas.
- Though they cost more to install, geothermal heat pumps are the most efficient choice. The units can also last more than 20 years, while air-source heat pumps last between 10 and 20.
- Energy Star heat pumps and geothermal heat pumps may be eligible for tax credits. Check with your state and with energystar.gov for current requirements for tax credits.
