Heat Pump vs. Air Conditioner: What Changes When You're Replacing an Existing System?

If you're building a new home or replacing an entire HVAC system, you can plan around either option. Replacing just an existing air conditioner is a little different because you already have equipment installed that you may want to keep.

A traditional central air conditioner does one job. It removes heat from inside your home and transfers it outdoors. When temperatures drop, your furnace or another heating system takes over.

A heat pump handles both heating and cooling. During summer, it works much like a conventional air conditioner. In winter, it reverses the process, pulling heat from outdoor air and moving it indoors.

That means a heat pump can take over some or all of the work your furnace currently does. Here's how the two compare:

In many cases, yes. You don't necessarily need to tear out your entire HVAC system to make the switch.

Consider a typical home with a gas furnace in the basement, an evaporator coil attached to the furnace, and an outdoor AC condenser. The air conditioner needs replacing, but the furnace is still working fine.

One option is to install another conventional AC system and continue using the furnace for heat. Another is to install a compatible heat pump that handles cooling in summer and provides heat during colder months. The existing furnace could remain in place as a backup or alternate heating source.

That second arrangement is called a dual-fuel system. It sounds fairly straightforward, but the existing indoor equipment has to work with the new heat pump. A replacement isn't as simple as disconnecting the old outdoor unit and connecting a new one.

The indoor coil, controls, refrigerant piping, and heating configuration all need to be evaluated.

No. Switching to a heat pump doesn't automatically mean your gas furnace has to go. In fact, keeping the furnace can be a practical option, particularly if it's relatively new and still in good condition.

Keeping Your Furnace as Backup Heat

In a dual-fuel system, the heat pump provides heating during certain outdoor conditions. The furnace takes over when the controls determine that gas heating is the better option. For example, your heat pump might handle heating during a cool fall afternoon, while the furnace takes over during a particularly cold winter night.

The exact changeover point depends on the equipment, local climate, energy costs, and how the controls are configured. You also need to make sure the furnace blower and indoor coil can work with the new heat pump.

Keeping the furnace may save you from replacing equipment that still has years of useful service ahead of it.

Replacing the Furnace With an Air Handler

You can also use a heat pump with an electric air handler instead of a gas furnace. An air handler circulates heated or cooled air through the ductwork. In a heat pump installation, it works with the indoor refrigerant coil and may include supplemental electric heating.

This setup eliminates the need for a furnace as the primary or backup heating source, although supplemental heat may still be needed. It's a bigger change than replacing the outdoor AC equipment. Your installer will need to evaluate the electrical supply, heating requirements, airflow, and ductwork.

If your furnace is already nearing the end of its useful life, this may be a good time to compare both options.

Here's something that surprises many people shopping for replacement equipment online.

Your outdoor air conditioner might be rated at 3 tons, and the heat pump you're considering might also be rated at 3 tons. That doesn't mean you can connect the new unit to your existing indoor coil.

The indoor coil is part of the refrigeration system. With an air conditioner, it absorbs heat from the air inside your home. With a heat pump, it also has to work during the heating cycle.

Not every indoor coil is suitable for both applications. Refrigerant type, coil capacity, metering components, and manufacturer-approved equipment combinations all affect compatibility. This becomes especially important with older systems. A new heat pump may use a different refrigerant than the equipment currently installed.

In some replacements, the indoor coil will need to be changed even if the existing furnace stays.

Before purchasing an outdoor heat pump, have your installer confirm which indoor components can be reused and which need replacing.

Your current thermostat may not be suitable for a heat pump. A typical furnace and air conditioner setup has separate controls for heating and cooling. A heat pump uses the refrigeration system for both, which requires different control functions.

If you're keeping a gas furnace, the thermostat or associated controls also need to manage when the heat pump runs and when the furnace takes over.

Some heat pump systems require specific compatible controls. This isn't usually the most expensive part of a replacement project, but it can cause problems if it's overlooked.

A thermostat that works perfectly with your existing AC and furnace isn't necessarily compatible with the new equipment.

That depends on the heat pump, your home's heating needs, and the temperatures where you live. Modern heat pumps can operate in cold weather, but their heating capabilities aren't all the same.

A heat pump that works well in a mild climate isn't necessarily the best choice for a home where winter temperatures regularly drop well below freezing. Some equipment is specifically built for colder conditions. Other systems are better suited to milder weather or installations with supplemental heating.

Here's an important distinction.

A 3-ton air conditioner and a 3-ton heat pump may have similar nominal cooling capacities. That doesn't tell you how much heating capacity the heat pump will deliver on the coldest days of the year. Heating performance changes with outdoor temperature, and equipment specifications should be reviewed at the temperatures relevant to your location.

If you're planning to keep your furnace, it can provide heating when the heat pump isn't the preferred option.

If you're removing the furnace, your installer needs to determine how the system will meet your home's heating needs during cold weather.

Buying HVAC equipment online gives you the opportunity to compare models, specifications, and pricing before making a decision.

But if you're converting from conventional AC to a heat pump, start by having your installer look at the equipment already in your home. You'll want answers to a few specific questions:

• Is the heat pump properly sized? Your existing AC tonnage is a useful reference, but the replacement should be selected based on your home's heating and cooling requirements.

• Can the existing furnace stay? If so, confirm that its blower and the proposed indoor equipment are compatible.

• Does the indoor coil need replacing? The new heat pump must work with an approved indoor coil and refrigerant configuration.

• Can the existing refrigerant lines be reused? Their size, condition, and suitability for the new equipment need to be checked.

• Will the electrical system support it? A heat pump or new air handler may have different electrical requirements than your current equipment.

• What controls are needed? The thermostat and any backup heating controls must support the new configuration.

It's worth getting these details sorted out before placing an order. Finding a heat pump at an attractive price doesn't help much if it can't be installed with the equipment you intended to keep.

Sometimes. But the outdoor unit's price doesn't give you the full picture. Let's say you're comparing two replacement options. The first involves installing a new conventional air conditioner and matching indoor coil while keeping your existing gas furnace.

The second involves installing a heat pump, replacing the indoor coil, updating the controls, and configuring the system to work with that same furnace. The heat pump project may involve additional equipment and labor.

Now consider a different situation. Your air conditioner and furnace are both old, and you're planning to replace everything. In that case, comparing a conventional AC and furnace combination against a heat pump with an air handler makes more sense.

The cost difference could look quite different as there are operating costs to consider, too. A heat pump uses electricity for heating, while a gas furnace burns fuel. Which one costs less to run depends on local utility rates, equipment efficiency, winter temperatures, and how much each heating source operates.

Ask your installer for a comparison of the complete installed systems rather than comparing outdoor equipment prices alone.

There's nothing wrong with choosing another conventional air conditioner. If your gas furnace works well, you're satisfied with your current heating arrangement, and you want a relatively straightforward cooling equipment replacement, sticking with central AC may be the more practical choice.

A heat pump becomes more interesting when you're also thinking about how your home will be heated. Maybe you'd like the option of heating with electricity. Maybe you're already planning to replace the furnace. Or perhaps you want to keep your existing furnace but have the heat pump handle heating during milder weather. Those are reasonable reasons to explore a change.

Just remember that adding heating capability changes more than the outdoor equipment. You need to look at the complete system before deciding.

If your existing air conditioner needs replacing, a heat pump is worth considering. You could gain an additional heating option without necessarily removing a working furnace.

But don't choose replacement equipment based on matching tonnage or a similar-looking outdoor cabinet.

Have your HVAC installer check the existing indoor coil, furnace or air handler, refrigerant lines, and controls. Once you know what equipment will work together, you can make a more useful comparison of heat pump vs. air conditioner pricing.

Public HVAC Solutions carries heating and cooling equipment for residential and commercial applications. You can browse available models, review specifications, and compare equipment options before making a purchase.