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February 8th, 2023
According to the Department of Energy, heating your home typically represents about 45% of your utility bill.
When you’re trying to lower your energy bill, you can resort to the common remedies: open the blinds on sunny days so that you can receive solar heat; put up weatherstripping around leaky windows and doors; increase the insulation in the attic; and so on.
But one question seems to be on many homeowners’ minds when we talk to them about their energy bills: Is a high-efficiency furnace worth it?
In other words, if you’re tired of your existing furnace’s increasingly high repair bills, and you’re thinking about buying a new one, you can opt for several choices.
One big distinction between models is those with standard efficiency, and those labeled high efficiency. Clearly, there’s a difference. And those who haven’t bought a major piece of an HVAC system might need to be reminded that there’s no small investment when you’re talking about a major piece of machinery.
Even the cheapest models cost thousands of dollars. The most expensive ones are double that but are more technologically advanced. So is it worth spending big?
If you’re wondering if there’s an easy answer, there isn’t. But by the end of this article, you’ll have a better idea of how best to spend your money.
How Are Furnace Efficiencies Rated?
AFUE stands for Annual Fuel Utilization Efficiency. It’s kind of like miles-per-gallon (MPG) for cars. It’s a standard measurement of how efficiently a furnace converts energy from the fuel it uses into warm air for your home.
It is measured in percentage points; the higher the number, the more efficient it is. For instance, an 80% furnace turns eighty cents out of every dollar into creating heat. The other 20% is vented out of the house, usually through a flue.
What Is a Standard-Efficiency Furnace?
The current minimum AFUE set by the Department of Energy is a rating of 80% for gas furnaces, and is called standard efficiency. These furnaces are non-condensing units that have a primary heat exchanger, a metal inducer, and a metal flue pipe.
They usually include fans that control the flow of combustion air and gasses, and typically have electronic ignition instead of a pilot light. After combustion takes place in the heat exchanger, a fan blows the hot air through the ductwork.
The flue gas, which is comprised of residual substances such as dust, sulfur oxides, nitrogen oxides, carbon dioxide, and carbon monoxide, is hot enough that it is vented up and out of the house through the flue as steam.
If 80% sounds like a waste of energy, compare that to an old furnace that has pilot lights and natural draft induction. (This method allows warm air to rise through pipes, which direct the warm air into floor or wall vents.) In general, their AFUE ranges from 56 – 70%. At 56%, efficiency, almost half of the money you put into heat leaves your house as waste.
What Is a High-Efficiency Furnace?
The 1980s introduced “high efficiency” to the lexicon. The National Appliance Energy Conservation Act of 1987 required all new furnaces to be at least 78 percent efficient.
Today, in terms of AFUE, 90% and higher is the threshold for a high-efficiency furnace, which is a condensing furnace.
High-efficiency furnaces have a primary and a secondary heat exchanger. When this furnace runs, it pulls so much heat out of the flue gas that it condenses and produces water, which goes down the drain via a PVC pipe.
The installation of high-efficiency furnaces includes changes to your existing venting (it will be capped) and the installation of a condensate line. One small wrinkle is that the condensate drain system needs to be free of clogs. Homeowners can clear this themselves or have an HVAC contractor do it while they perform annual maintenance.
How Much Money Could You Save with a High-Efficiency Furnace?
Now we get to the math. A standard-efficiency furnace returns 80 cents to the dollar you put into it. A high-efficiency model returns at least 90 (and most models are rated at between 92 and 98%).
So you get 10-18 cents to the dollar every time it runs. Your fuel bill, as we’ve mentioned, is about half of the total energy bill. That adds up. I tell people that they can expect to pay off the difference between the initial costs of the two furnaces in four to seven years.
Of course, there are dozens of factors in this equation. How often do you run it? What’s the climate like during the winter? What is the thermometer set to? Do you take extra steps to winter-proof your home? How many occupants will be living there? And so on. Putting an exact number on your savings is a moving target.
One question we ask customers before we make a recommendation is, “How long do you expect to be in your home?” If you’re planning on moving away in a year or two, it makes no sense to decide on a high-efficiency furnace. The payoff isn’t worth it.
But if you’ll be in your home long-term, the efficiency will pay off. The bigger the house, the bigger the furnace, the more you’re going to save.
And if that’s not enough, there are other benefits.
Read more: The Complete Guide to Home Furnaces
The Biggest Benefit of a High-Efficiency Furnace
Comfort. Plain and simple. You’ll thank yourself because this furnace satisfies your need for temperature and humidity control, and indoor air quality. You’ll breathe better. Your energy bills will be lower. Those uneven temperatures that you’ve put up with will disappear. Your HVAC system will provide you with the comfort you deserve.
More Benefits of a High-Efficiency Furnace
An efficient furnace will run longer at a slower speed. The more it runs, the better the air will mix, helping to eliminate hot and cold spots.
- Less noise: If the furnace is running at a slower speed, that reduces the fan noise as well as the amount of air in your ductwork.
- Better indoor air quality: The more the air moves, the better your furnace’s air filter will catch impurities. You get a less dusty home with fewer other impurities.
- Better for the environment: The less natural gas or propane you burn, the more green you are. You’re using less fuel, and you're creating less carbon dioxide, which is a greenhouse gas.
- Extra rebates: Buying a high-efficiency furnace may qualify you for additional rebates, especially if you choose one that’s Energy Star qualified.
- May be compatible with smart thermostats: High-efficiency furnaces tend to come equipped with a two-stage or modulating gas valve as well as a variable-speed motor. Your smart thermostat can talk to both of these, and can regulate the amount of heat so that it remains steady whatever the outside temperature.
Modulating gas valves and variable-speed motors require a bit more explanation:
What Is a Modulating Furnace?
Gas furnaces come in stages, which is a fancy term for the amount of heat they can produce. A single-stage furnace means that it is either off or on at 100%. These are the cheapest option.
A two-stage furnace has two “on” options. One is at 100%, the other is at 60-70%. A reduced option of heat circulates the air better and cleans the air better, as well. It’s also more energy efficient.
A modulating furnace can produce almost any level of heat. It is the best (and most expensive of the three) at keeping the indoor temperature at a fixed setting, circulates the air the best, and is the quietest.
Read more: Single-Stage, Two-Stage, and Modulating Furnaces: Differences and Benefits
What Is a Variable-Speed Fan?
Like stages, the speed of the fan (also referred to as the motor) that blows the heat through the vents comes in three varieties.
A single-speed is with on at 100% or off. This technology has been around for decades and decades, and is the cheapest option.
A two-speed fan operates at around 60% of capacity, 100%, or it’s off. At its reduced level, it moves less air but runs longer. This has several advantages. It’s easier on the equipment since it’s not starting and stopping so often. The longer run time allows warm air a better chance to mix with the cold. It filters the air better, leading to enhanced indoor air quality. Your ducts will be quieter, since not as much air is moving, and the slower speed will make the fan less noisy, as well. It’s also easier on your energy bill.
A variable-speed fan is what the label suggests. It can operate at almost any speed, able to deliver a little bit of heat when that’s all the thermometer calls for. It’s more energy-efficient, quieter, and a better air cleaner. It’s also the costliest.
Read more: What Are the Benefits of a Variable-Speed HVAC Motor?
Buying a High-Efficiency Furnace in Columbus, Ohio
There’s nothing black and white when you talk about an HVAC system. From the type and size of the air conditioner to the capacity and fan speed of the furnace, to the ventilation system (or ductwork), they all depend on one another to keep your house comfortable.
To get the best possible outcome, a furnace needs to be able to communicate with the thermostat correctly, and must have properly-sized ductwork. Ditto with an air conditioner, which relies on the furnace (or air handler) to distribute the conditioned air.
Good HVAC salespeople can put the pieces together for you, and they should do it in a way that’s not overwhelming. We hope to have laid out some terminology and choices so that you can spend your money wisely.
If you’re in the market for a furnace, high- or standard-efficiency, we’d love to hear from you. Fill out the box below with your zip code to see if you’re in our service area. We hope to hear from you soon.
