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Do You Have to Replace Your Heat Pump and Furnace at the Same Time?

Heat pumps don’t always rate with air handlers or furnaces. Depending on the make and model, a homeowner may have to invest in a new HVAC system.

Do You Have to Replace Your Heat Pump and Furnace at the Same Time?

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Bryan Carnahan


February 20th, 2023

We try to solve problems. Too much humidity? We have an answer. Is your furnace making strange sounds and your energy bill seems high? Talk to us; together we can find a solution that’s beneficial to both of us.

We always discuss comfort concerns with our customers so that we can identify where the pain points are. Whether it’s a room that’s hot and sticky in the summer, or an air conditioner that seems to be getting louder and louder, we strive to identify the biggest obstacles to your comfort. Because comfort is everything.

Comfort means no worries. As the Disney characters would say, “Hakuna Matata.”

Yet, once in a while, we are the bearer of bad news. You might be in the market for one piece of equipment and have done your research into the price, but you hear from us that replacing one unit means replacing two.

It can be a shock to you and your budget.

If you’re reading this article, you might have one pressing question that needs to be answered: Can you just replace your heat pump, or do you need a new furnace/air handler as well?

The answer, like so many about HVAC systems, is maybe. But we can provide you with the tools and information you need to make the right decision for you.

Read more: Heat Pumps 101: The Ultimate List of Heat Pump FAQS

Heat Pumps in Central Ohio

Heat pumps are not common in Central Ohio. Fire & Ice’s sales of heat pumps versus air conditioners are 15-20% at best. They tend to be more popular in the southern United States, where a cold day means 40 degrees Fahrenheit.

In the summer, they are just as efficient and can cool as well as any compatible air conditioner. It’s in the winter that they can seem inadequate. Once the temperature falls below 40 (depending on the make, model, and style), they can “derate,” meaning that they struggle to turn cold air into hot.

As a result, the homeowner may feel cool air coming out of the ductwork.

Then one of three things happens, depending on whether you have a gas, oil, or propane furnace; an electric furnace; or an air handler equipped with electric heat strips.

  • Heat pump paired with a fuel furnace: This is called a dual fuel system, meaning that there are two sources of fuel being used. Electric is powering the outside unit and natural gas (or propane or oil) is taking care of the inside. The furnace will take over the heating duty when the heat pump cannot. This may be automatically controlled through your thermostat, or you may have to flip between the two manually.
  • Heat pump paired with an electric furnace. The heat strips for an electric furnace will take over. Electric furnaces are considered to be 100% energy efficient, but bear in mind they can actually cost almost 2.5 times more than a typical heat pump to put out the same amount of heat.
  • Heat pump paired with an air handler. The air handler takes over. The air handler needs to be equipped with heat strips for this to happen.

Read more: Can a Heat Pump Replace My A/C and Furnace?

Why Would You Need a Heat Pump in Central Ohio?

Central Ohioans have heat pumps in certain scenarios. There are some areas in Columbus that are all electric. A natural gas line may not be on the main road, and the cost of oil can be prohibitive. (Technically you could have an air conditioner paired with an electric furnace or air handler as your primary heat source. It’s not a good idea because of the expense.)

The other scenario we see is propane furnaces. If you have a propane system, it is wise to have a heat pump rather than an AC because propane can be expensive.

How expensive? According to Advanced Propane, Inc:

  • A 2,000-square-foot home in a “mild” climate—southeast or southwest United States—would require approximately 2 million BTUs of propane and cost about $76 on average per month to heat.
  • A home in a “moderate” climate—somewhere such as North Carolina, Tennessee, or Kentucky would require 4.0 million BTUs, and cost about $152 per month on average.
  • A home in a severe climate—Maine, Vermont, New Hampshire, the Upper Midwest, or Rocky Mountain states would need around 6.5 million BTUs and cost around $248 per month on average to heat.

On rare occasions, you’ll have folks who have natural gas and they have a heat pump because they want to be greener. (Even the greenest of gas furnaces produce some waste.) Or they’ve invested in solar panels, so they want to take advantage of the cheap electricity.

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What Happens to Heat Pumps in the Winter?

Heat pumps are outside, and they’re going to freeze up when it gets too cold because they’re trying to convert cold air into heat. If you put your hand over an air conditioner, you’ll feel hot coming from inside the house. If you do that to a heat pump while it’s heating, you’ll get cold air. When cold air outside combines with cold air from inside, it freezes. When it freezes, it can’t run anymore.

This is Columbus. We have winter. Unless you have a high-efficiency heat pump, your emergency heat will need to be working when it’s 20 degrees out.

Here, we have winter for at least two months. So you’ll have between 40-60 days at a minimum that you’ll be below 40 degrees.

Technically, manufacturers say modulating heat pumps can still work when it’s down to zero or negative 5. But it won’t be “hot” heat. If it has 36,000 British Thermal Units (BTUs) of heat potential, as it gets colder outside, it won’t be able to push that. It will be much less. The modulating heat pumps have a hotter discharge, much hotter than a standard, single-stage heat pump. But it will lose its capacity.

When it freezes up, it goes into defrost mode. That’s why you need emergency heat.

Once it defrosts and has another call for heat, it will try to go again and will run until it freezes up again. In the old days, you had a manual switch-over. The heat pump would defrost, but unless you manually switched it back over to see if it would go again, it would never try again.

New ones with new thermostats will operate the heat pump at a certain temperature until they switch over to emergency heat.

We can tell when we’re in homes when we ask customers what their electric bills are, if they respond $200+ dollars, we know that their thermostat is set to emergency heat. It’s expensive.

Which Furnace Pairs Best With a Heat Pump?

In Ohio, due to the cheaper cost of gas over electric, we recommended going with a gas furnace over an electric system. If you have natural gas access and can get a meter on your house, gas is better than electric. Gas is hotter than electric because it’s fire. Depending on the system, it comes out at around 140, 150 degrees. A regular heat pump will produce as low as 85. That’s why they say heat pumps give off cold heat. It never feels as warm as a gas system does.

The most efficient system would be dual fuel - a natural gas furnace with a modulating heat pump. The gas will kick in when it gets too cold (it’s efficient because heat pumps are 100% efficient.) That would carry the load during the mild part of winter, during which natural gas won’t have to be used at all. But when it needs help, instead of heat strips in your basement, you have warmth generated by fire. So you’re going to have a much hotter heat, and it will be much cheaper.

The only time I get pushback from that suggestion is when a customer says, “I don’t want any carbon footprint.” Even the most efficient gas furnace has some exhaust. To eliminate any waste, the HVAC system would need to be all-electric supplied by solar panels.

When Would You Have to Replace Both a Heat Pump and the Inside Unit?

If you have a communicating outdoor unit, you have to have a communicating indoor unit.

A communicating heat pump has multiple heating and cooling stages. They can ramp up or down in coordination with the thermostat to provide optimal comfort to a home. The indoor temperature remains constant no matter what the outside temperature is.

The problem occurs when one piece of the HVAC system doesn’t have the communicating technology. It negates those that do. You wind up with a system that becomes rudimentary, unable to function as one unit.

If you have a two-stage heat pump or above, it has to go with something that will rate with that. If it’s communicating, it must go with a communicating system or it won’t work.

And it would not be covered by a warranty.

The furnace doesn’t need the air conditioner or heat pump to function, but the heat pump does need the furnace. The furnace’s blower circulates the conditioned air through the ductwork.

If you have a single-stage heat pump, it can go with any furnace.

If it is an add-on heat pump, which means that you have a heat pump and then you have an air handler/furnace, and you have a separate piece of equipment, which is the coil, then no, you don’t have to replace both. All you have to do is make sure that the furnace “rates” or matches the capabilities of the heat pump.

If there is a fuel source (oil, gas, or propane), then you do not have to replace the furnace as long as it rates with the heat pump.

If it’s all-electric, you must replace both.

We get pushback from homeowners when we tell them the bad news. They tell me, “Well, my air handler is fine.” That could be 100% true. Customers might go to our website and see how much a heat pump costs. But that’s not the end of the conversation.

We are honest and upfront with our customers, so we might have to also tell you that your furnace or air handler needs to be replaced as well, adding to the total cost.

Do we see homes where there are mismatched units in place? Yes. Is it the wrong thing to do? One hundred percent it’s the wrong thing to do. If you want it done wrong, there are plenty of HVAC contractors who will do it wrong. We would never do that because we could never guarantee it.

Replacing a Heat Pump in Columbus, Ohio

Replacing a piece of a heating and cooling system can be a difficult decision. To make it easier, you should meet with a salesperson who listens to your unique situation and unique concerns about your unique home.

If you’re in the market for a new heat pump, we hope we passed on some useful information so that your decision process can be a little easier.

And if you’d like to talk to someone from Fire & Ice, we’d like to talk to you, too. Fill in your zip code in the graphic below to see if you’re in our service area.

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