What Is a Dual Fuel HVAC System?

If you’re considering replacing your electric furnace with a gas (or propane) one to take advantage of your heat pump’s capability to heat, you are entering the realm of dual fuel.

As with other HVAC decisions, there are positives and negatives. Considerations include:

• What is the initial price to set up a dual fuel system?
• Will your utility bills go up or down?
• What is the environmental impact?
• Is it worth it in the long run?

There are myriad issues that should be considered when deciding whether to go dual fuel, and it’s natural to feel overwhelmed by all the information available.

That’s where we come in.

On your journey toward comfort - both physical and financial - I’m here to provide answers. Fire & Ice has installed thousands of heat pumps, air conditioners, and furnaces in Columbus, Ohio, and we’re happy to share our knowledge.

By the end of this article, we hope that you will understand a bit more about dual fuel, and know whether it’s right for you.

What Is Dual Fuel HVAC?

Dual fuel means that you use an electric heat pump with a gas (or propane or oil) furnace. (And, yes, technically a gas furnace with an electric AC or heat pump is dual fuel, but we don’t call it that.) It means that there are two heating sources that alternate between two fuel sources.

In a traditional gas system, you’re using only the furnace for heating, and you’re using only the AC for cooling. Dual fuel means you’re using your heat pump for heat first, with your gas furnace as back-up. You’re going to let the heat pump do its heating until it gets too cold, then the gas furnace will turn on as a secondary heat source.

When Is a Dual Fuel System Recommended?

If you have a propane furnace, I’d recommend going dual fuel. The same goes if you have an oil furnace.

There are two other reasons to do dual fuel. One: The homeowner wants to be very “green.” An electric system has no emissions, so you want to use electricity on the heat pump as much as possible regardless of the expense. They use the gas furnace only as necessary. (Something to consider: Some electricity comes from coal, which is one of the dirtiest fossil fuels.)

The other reason to go with dual fuel is homeowners think that natural gas might skyrocket in price, as it did in the 1970s. According to the U.S. Energy Information Administration, the U.S. price of natural gas, measured in dollars per thousand cubic feet, went from $1.09 in 1970 to almost triple the price in 10 years, to $2.98.

More than likely, a jump in price is not going to happen. In my opinion, the price is so low now, you’re going to need a new system by the time that natural gas prices would skyrocket and make it prohibitive to use natural gas.

If you have natural gas, the best reason to do dual fuel is you have very cheap electricity because you have solar panels.

What Are the Initial Costs Associated with a Dual Fuel System?

The first step on the road to dual fuel is to contact your natural gas provider.

According to homeguide.com, “Gas line installation costs $12 to $25 per linear foot. The cost to run a gas line from an existing connection is $355 to $743, while adding a pipe from the meter is $500 to $2,000. Converting to natural gas or installing a new line from street to house costs $2,000 plus.”

Then you’ll need an HVAC expert to hook the line up to your furnace. Also essential is a flue pipe or chimney to exhaust the combustion byproduct.

If you’re leaning toward propane, an above-ground 500-gallon propane tank averages $700 to $2,500 according to fixr.com. If it’s installed below ground, a tank costs between $1,500 and $3,000. Then you’ll need a line into your home, plus the connection to your furnace, plus the cost of filling it.

Heating and Cooling with a Dual Fuel Heat Pump

During the summer, the heat pump works as an air conditioner. Working in tandem with your furnace, it removes hot air from your home and expels it outside while cooler air is distributed by the furnace’s blower.

During cooler months in spring and fall, the heat pump can supply warm air while the furnace remains ready to provide even warmer heat. Depending on the efficiency and fan of the heat pump, it starts to provide less and less heat as the temperature drops to 30 degrees Fahrenheit and lower.

As long as the temperature outside is above 35°F or so, a heat pump can pull heat from the outside air for less than it costs to fire up the furnace. The furnace kicks in for only the coldest months.

Even when it’s cold outside, a decent amount of heat is available.

During cooler seasons such as fall and spring, the heat pump handles the heating duties solo. The dual fuel system still incorporates the furnace, but it does it without using any burners; it uses its blower only.

What’s the Advantage of a Dual Fuel HVAC System?

Typically the advantage of a dual fuel system is if you have natural gas and solar panels. If you have solar panels, your electricity is very cheap. So why not use as much electricity as you possibly can (electric powering the heat pump) before you use something that you’re paying for (gas furnace)?

The bigger reason it’s used is you don’t have natural gas but you have propane or oil. If you have propane, we normally do dual fuel because you can have your heat pump do most of the heating so you’re not draining your propane tank all winter long.

It’s like grilling at your house using propane. The worst thing in the world is you turn on your grill and there’s no propane there, right? With dual fuel, if the tank runs low at the end of the winter, and you don’t want to fill it yet, you still have a heat source with the heat pump.

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Who Could Benefit From a Dual Fuel HVAC?

If you currently have an all-electric system, you probably wouldn’t go to a dual fuel unless you want to buy a propane tank. If you have an all-electric system and you go to dual fuel, the upfront cost will be much more expensive, because now you have to pipe in propane, oil, or natural gas in addition to creating a vent for it.

Long term, winters with a propane furnace are typically going to be less expensive than electric unless you’re going to go with a super-high-end heat pump. So with a dual fuel system, you don’t have to get a high-efficiency heat pump because you have a gas system.

If you buy a 14 SEER heat pump (SEER is a measure of efficiency) and you have an electric system, the heat strips (also known as emergency or backup heat) in the electric furnace are going to go on a lot. If you use a propane furnace, the fuel bill is going to be less expensive than an all-electric system.

Related content: What’s a Good SEER Rating and Why Does It Matter?

Propane is going to burn hotter, and the fire from the furnace makes the house warmer quicker than electric.

If you did a standard all-electric system, the heat pump will give you cool heat. It comes out at 80-some degrees.

A variable-speed heat pump can produce heat that comes out at a much higher temperature. It feels more like a gas system. For comparison, the heat of a gas furnace comes out at something like 145 degrees.

You don’t have to invest in a high-end heat pump if you have a gas system. The outside temperature could drop to 35, 40 degrees, and then the gas system would take over. Your upfront cost would be cheaper on equipment if you settle for an entry-level heat pump, which ranges from $4,900 - $7,000.

How Much Does a High-End Heat Pump Cost?

If you want your heat pump to do as much work as possible, it needs to be high-end, which costs anywhere from $6,500 - $12,500.

That sort of heat pump would have a variable-speed fan that could keep the unit running even if the outside temperatures get below freezing.

A top-of-the-line model such as the Trane XV20i can operate down to about negative 5 degrees. It won’t be at full capacity, but it can still provide some heat.

Environmental Impact of a Dual Fuel System

Anytime something burns - whether it’s gas, propane, or oil - there will be a byproduct that will have to be vented outside. One of the more noxious gases created by this combustion is carbon monoxide, an odorless, colorless gas that can cause serious health concerns.

A typical gas furnace gets an AFUE rating of 80, which means that 80% of the heat created goes into your ducts. Twenty percent becomes waste. High-efficiency furnaces can go up to 98.

Electric furnaces are 100% efficient, with no by-products.

Exploring More Options About Dual Fuel

The next step for you depends on where you are in the process of making your home comfortable. Some homeowners I speak to have done all the necessary research and are ready to pick out their HVAC equipment, which can be installed within the same week. Others don’t even know what will be involved in the process.

We try to help both types of customers, but the best way to make progress is to help yourself by being proactive in getting the information you need.

Do some research, form a budget, plan a timeline, and make some calls to secure the help you’ll need for every stage of the process.

At the end of the line, you’ll have a brand new, comfortable, and efficient HVAC system that will last you for years or even decades. If that’s worth it to you, I hope that Fire & Ice can be a part of that journey.

To aid in your research, here are a few articles about gas furnaces and heat pumps:

How Much Does a Heat Pump Cost to Replace in 2021?

Cost of an Air Conditioner Replacement in 2021, a Complete Breakdown

Trane Gas Furnace Guide: 2021 Pricing & Product Reviews

If you’re ready to schedule an estimate, get started below to see if you’re in our service area. I’m looking forward to helping you convert to a more comfortable home.