How to Tell If Your Furnace Efficiency Is Too Low

My neighbor Rick is quite the guy. Every morning at the crack of dawn, without fail, he goes for a ten-mile run. Not only that, he runs two marathons every year.  

Last week I was up early and saw him stretching on his lawn after one of his runs, so I poured him a cup of coffee and brought it out to him. Naturally, we got to chatting about how he stays so darn dedicated to his training. The key, he told me, was consistently tracking and evaluating his performance.

Now, I only run once in a while, so I couldn’t really relate to this caliber of daily dedication to monitoring his efficiency. But as I stood out in the cold, I got to thinking about furnace efficiency and how monitoring a furnace’s performance is sort of similar to how Rick monitors his efficiency as a runner.  

When I told this to Rick he was intrigued. Like many homeowners, he knew nothing about furnace efficiency and had no idea how to optimize it. In the spirit of being neighborly, I filled Rick in on how to tell if your furnace efficiency is too low—and what to do to make sure it’s running as efficiently as possible during the chilly Northern California winter.

How to Tell If Your Furnace Efficiency Is Too Low Based on AFUE Ratings

When I was discussing furnace efficiency with Rick, I explained to him that every furnace has an efficiency rating called the Annual Fuel Utilization Efficiency (AFUE) rating. This number indicates how much heat your furnace produces compared to how much energy is required to produce that heat. For example, if your AFUE rating is 87, this means that 87% of the energy used by your furnace actually produces heat, and 13% of the energy is lost in the process—which on the surface sounds fairly efficient.

It’s wise to know the AFUE of your furnace so that you have a general idea of how efficient it should be but, it’s important to keep in mind that some heat will also be lost through your ductwork and the AFUE doesn’t account for this. Unless you’ve had your ducts sealed and maintained or replaced recently, I generally say that about a third of the heat produced by your furnace will be lost through cracks and gaps in your ductwork.

Common Signs and Symptoms That Your Furnace Efficiency Is Low

My point in explaining that you can’t just rely on the AFUE rating to estimate your furnace’s level of efficiency is to show that it’s difficult to know exactly how well your furnace is performing—it isn’t as simple as recording your time when you get back from a run.

But, you don’t necessarily need to figure out your AFUE rating and calculate heat loss from your ducts in order to know if your furnace isn’t running as efficiently as it should be. It has some common symptoms to let you know when it’s struggling.

Here are a few telltale signs that your furnace efficiency may be on the low side:

• Your energy bills seem to be getting more costly
• It takes a long time for your house to heat up
• You haven’t changed your filter in over six months
• You haven’t had your furnace serviced in the last year
• Your furnace is more than 12 years old

If any of these things are ringing a bell, it’s a safe bet that your furnace isn’t running as efficiently as it could be. Luckily though, there are several simple things you can do to increase the efficiency of your furnace and make sure that you’re maximizing its AFUE to save money on your next energy bill.

Homeowner Habits to Increase Furnace Efficiency

Making sure your furnace is running efficiently may not take as much daily dedication as tracking your efficiency as a runner, but it does take some time and attention from you—and, every so often, a little TLC from a seasoned HVAC professional.

Here are some of the most important things you can do to ensure that your furnace is running as efficiently as my neighbor Rick:

• Change the filter every month: When your furnace filter is clogged with dust and debris, it has to work a whole lot harder to draw air in, causing it to eat up more energy and even to short cycle. Switching out your filter for a new one every month is the simplest thing you can do to help maximize your furnace’s efficiency.
• Listen for odd noises: I always tell homeowners to have a listen to their furnace every so often to make sure it isn’t making any strange sounds. If it is, it most definitely isn’t running as efficiently as it should be. Clanking, chirping, or booming sounds often indicate a problem with your furnace that needs professional attention as quickly as possible.
• Schedule regular HVAC checkups: It truly is amazing what biannual HVAC servicing can do for your system. In addition to having your AC checked in the spring before you turn it on for the summer, it is really important to schedule fall furnace maintenance before you rev it up for the winter. An experienced HVAC pro will be able to do a thorough inspection of the furnace and fix any problems that they come across. Not only does this help ensure that your furnace will run at peak efficiently all winter long, it will keep you and your family safe. As a bonus, fixing small problems before they become larger ones will save you big bucks in the long run.
• Invest in new HVAC energy efficiency tech like smart thermostats: I love smart thermostats because they can really help your furnace run more efficiently—without you even having to think about it! Pre-programming your thermostat to cooler temperatures at night and using your smartphone to adjust the temperature when you are out of the house during the day can save your furnace a lot of unnecessary energy output.

Remember, furnaces are tricky creatures so knowing when to call a seasoned HVAC professional is key to optimizing your furnace’s efficiency. I typically caution everyone from tampering with their furnace on their own, as it can be dangerous and cause more harm than good.

In the end, my neighbor Rick and I ended up helping each other out. I’ve started to work on increasing my efficiency as a runner and he’s taking the necessary steps to make sure his furnace is as efficient as possible. And while it may not be as big of an accomplishment as running a marathon, taking the necessary steps to ensure your furnace is efficient certainly pays off when it comes to your energy bills—and will certainly extend the lifespan of your furnace.

At Bell Brothers, we believe in the whole home approach to health and efficiency. Our trained HVAC professionals would not only be happy to give your furnace a little love, we’d love to make sure your windows, insulation, and ducts are also working efficiently to keep your house warm this winter. Contact us today to schedule your fall furnace servicing.

Wondering how to finance a new furnace, or maybe even new windows and plumbing? HERO is a unique financing option that helps California homeowners afford energy efficient upgrades to their home. Contact Bell Brothers, a HERO-approved contractor, to learn more. Our local HVAC, plumbing, and window specialists will walk you through the entire process, from applications to installation.

Image courtesy Unsplash user Kari Shea