What features should I look for and what efficiency makes sense?

I’m trying to decide on the best new furnace for my home. I need a forced air gas furnace to replace a Goodman furnace that has an incredibly noisy fan. It still works but now that winter is wrapping up I think it’s time to replace it. What features should I be looking for in a furnace and should I go for mid- or high-efficiency?

Answer from Green Energy Efficient Homes

Update for 2021: The best new furnace for everyone isn’t a furnace at all, it’s a <i>heat pump</i>. I can no longer in good conscience recommend anyone purchase a furnace, given the climate emergency and the need for all of us to reduce our carbon footprint as quickly and as much as possible. See my entire new section on heat pumps for lots of helpful information on why heat pumps really are not only the more environmentally friendly choice, but the more cost effective choice in the long run. Beyond this, much of the advice in this article still applies: find an installer you trust (of course, if you do decide to go for a heat pump, you’ll need to find an installer who offers heat pumps); choose the right product from their available brands, as energy efficient as you can, and consider a service contract (although these are less important for heat pumps than for furnaces, because heat pumps do not have combustion and therefore there are no corrosive exhaust gases that can damage components).

I would advise you to start your search for the best new furnace by looking for the best HVAC installer in your area. There is a great deal of fuss on the internet about the reputation of this or that furnace manufacturer and there is no shortage of negative reviews for just about all of them, while there are few positive reviews for any of them. There are two reasons why you’ll hear every homeowner complaining, and almost no one claiming they have the best new furnace:

  1. People write reviews when they’re upset about how their product is working (or when it stops working). So we see lots of negative reviews and few positive ones.
  2. Most HVAC problems are the result of faulty sizing, installation or servicing, not faulty or shoddy manufacturing. If you buy your furnace from the cheapest HVAC contractor, he is finding his profit by hiring cheaper labor or by rushing the install.

How do you find a good HVAC installer? First of all, keep an eye out for HVAC trucks in your neighborhood. If one is parked at a neighbor’s, visit that neighbor a few days later to ask how the install went and why they choose that installer. Ask your friends and relatives who they used and whether they were happy. Search on sites like homestars.com to find HVAC contractors in your area who have a good rating. (Read all their reviews though – and watch out for signs that a contractor is spamming reviews.)

Phone up prospective HVAC installers and ask them what products they offer and why you should consider using them. Ask them what they do to figure out the best new furnace for your needs. Ask them what they consider the best new furnace brands, and run a few brand names by them to get their opinion. Watch out for installers who bad mouth all the brands they don’t carry. Also ask any HVAC installer you are considering what awards or recognition they have received over the years, and follow up to verify the awards are legit. Ask any you are considering to provide you with at least three references, and phone those references.

Find out if the installer offers service contracts for the equipment they install, and how much the contract costs per year both during the furnace warranty period and afterwards. The best new furnace is one that doesn’t cost you a cent in unplanned expense in its first twenty years of operation – all you pay is the up front cost, and the annual maintenance and service fee.

Now that you’ve found an installer…

I really believe you should search for a good installer first, then look for the right furnace within the product lines they offer. Don’t be surprised if they don’t sell or install the furnace brand you want. After all, they specialize in one or two brands for a reason: they trust those brands and know them well. You wouldn’t want your Dodge dealer to service your Toyota, would you?

Things to look out for when buying the best new furnace include getting the right BTU output, as high an efficiency ration (ER) as you can afford, and additional features such as a variable speed, DC blower motor (more energy efficient and quieter), high quality air filter, and a decent humidifier. You should also decide up front, before upgrading to the best new furnace, whether you will soon want to upgrade your central air conditioner (or install a new one if you don’t already own one). You can get higher efficiency on both heating and air conditioning if you buy both your furnace and AC unit from the same manufacturer, since in some cases you can get a high SEER heat pump along with the furnace, that will heat the house when temperatures are mild outside (leaving the hard work on colder days to the furnace), and cool your house efficiently in hot weather.

BTU output: One of the things you should watch for when an HVAC installer comes to your home to do a quote, is how thorough a job they do of sizing your furnace. If they just eyeball it and tell you in five minutes that you need an 80,000 BTU furnace, don’t use them! You could wind up with a furnace that short-cycles (short bursts of heating that rapidly warm the place) or one that can never bring you up to a comfort level. The installer needs to do a heat load calculation, to figure out how much space you have to heat, how much heat will escape through walls, ceiling, and windows/doors, and therefore what BTU capacity you will need. When we had contractors estimate our new furnace in 1997 I had several quote me a price on a 60,000 or 75,000 BTU furnace without even walking around my house. The contractor I eventually selected told me a 40,000 BTU furnace was adequate – based on my modest heating needs (a thermostat setting a few degrees lower than most people use, and plans to continually upgrade insulation and windows). He said there might be a few days each winter when it takes the furnace a little longer to bring the house up from the programmable thermostat night-time temperature to the comfort temperature, but I would get better overall efficiency (and a lower installation cost) with the lower BTU furnace.

Efficiency Ratio (ER): You can buy mid-efficiency (80%+) or high efficiency (90%+) forced air furnaces. The best new furnace is a 96%+ efficient furnace, but how high should you go? Should you pay an extra $2,000 for that extra 16%? It might not seem to make economic sense. But my sense is that natural gas prices will continue rising over the next several years as more and more natural gas is used in electricity generation (to reduce our reliance on coal) and in the production of oil from the Alberta oil sands. So a savings of $150-200 a year on the high efficiency furnace today could translate into a savings of $300-400 a year five years from now.

Blower motor: One of the ways high-efficiency furnaces beat out their mid-efficiency cousins is by using a variable speed DC motor. Remember that your furnace uses electricity to blow the air around, and a DC motor tends to be more efficient than an AC motor. It can also continuously vary its speed to provide the right airflow for the heating needs of the moment. And a DC blower motor tends to require considerably less maintenance, and be much quieter than an AC blower.

Air filter: I recommend spending a little extra on a high quality air filter, such as the April Aire, since it provides much better dust removal and doesn’t require monthly changing. (We change ours once a year as part of our annual maintenance.) The more dust you can capture in the filter, the cleaner the air you breathe and the more efficient your furnace will be.

Humidifier: Finally don’t forget that when you turn on the heating, home humidity levels tend to drop, and the colder it gets, the dryer the indoor air becomes. This can lead to more frequent colds, and dryer air doesn’t do as good a job of transferring warmth from itself to your body. So make sure to include a humidifier as part of the furnace installation.

Our own furnace experience

To give you a concrete example of searching for the best new furnace, let me describe our own situation.

We bought our 1920’s home in 1997 and in our first heating season realized that the old oil furnace was very costly to operate. It had three things going against it: (1) The house stank of heating fuel; (2) We had to pay $300 several times over that first winter to refill the tank (the fuel oil rep told us the furnace was about 60% efficient); and (3) Our home insurance company told us they would not cover us after our renewal date if we didn’t get rid of the oil tank. So we were eager to replace the furnace with the best new furnace on the market – a gas furnace, since there was already a gas line to the house for the hot water heater.

After looking around for the best new furnace brand I narrowed the selection down to three or four models of high efficiency furnace in the 92-95% efficiency range. I contacted each manufacturer to find out which dealers in my area sold their high efficiency models. After a few calls to local installers, I settled on a company that is a good 25 miles away from my home but that really impressed me with their professionalism and thoroughness. They had won ‘Readers Choice’ awards consistently for almost a decade from their local community paper, they had a staff of over ten technicians as well as sales people and admin staff, and the owner himself came out and did a thorough assessment of our home heating needs. He recommended a high efficiency Carrier furnace that had an efficiency rating of 94%. That furnace cost us about $4000 at the time – a good $1200 more than an 80% efficient furnace would have cost – and at the time when I calculated the payback period, it was somewhere in the 15-20 year range. But I don’t regret the decision at all. Gas prices wound up rising faster than I predicted, and the extra efficiency has already paid for itself in reduced gas consumption. The best new furnace is pretty much always the most efficient one, as long as the installer has a good reputation, as mine did.

One thing to bear in mind with a high efficiency furnace is that no chimney flue is required – these things are so efficient that you can hold your hand in front of the exhaust tube (which normally exits a wall at basement level) and not burn your hand. So you’ll probably wind up with a couple of 2″ holes in an outside wall. Our installers vented the air intake and exhaust tubes out to the back of the house; unfortunately this meant we had tubes running nearly the full length of our unfinished basement, below the joists. We had this corrected a few years later when I dug out the basement and hired contractors to refinish it. They rerouted the exhaust pipes through the rafters and vented out a side wall, which kept the tubing out of the way.

Warranty and service: I strongly recommend buying a maintenance contract for your furnace and renewing it every year. If you add up those $60-120 a year payments it does work out to a fair bit of money over the lifetime of the furnace. But part of that cost is for a tuneup, which makes your furnace run more efficiently, and the maintenance contract means that no matter what goes wrong, repairs to the furnace are the financial responsibility of the installer, so you get a continually operating furnace at a predictable cost. You can reliably plan to keep a furnace for around 20 years, after which it is probably more sensible to replace it with a new furnace than to keep paying the ever rising maintenance contract fees.

And in the end… we got rid of our furnace in 2020, as well as our air conditioner, and we replaced both of them with a Carrier Infinity air source heat pump, and we’re now spending less money on utilities than we were before – and that’s factoring in adding charging an electric car to our utility bills as well. So my updated answer to what is the best new furnace, is – a heat pump!

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