HVAC Maintenance Guide: What to DIY and When to Call a Pro

Whether you have a gas furnace, a heat pump or something else, regular upkeep can save you money and keep your home's air cleaner.

Andrew King Contributor
Andrew King is an award-winning journalist and copywriter from Columbus, Ohio. He has covered sports, local news, entertainment and more for The Athletic, The Columbus Dispatch, Major League Soccer, Columbus Monthly and other outlets, and writes about home energy for CNET. He's a graduate of Capital University, and recently published a non-fiction book called "Friday Night Lies: The Bishop Sycamore Story" investigating the fraudulent high school football team that became the talk of the nation.
Andrew King
8 min read
A gray, dirty furnace filter.

If your furnace filter looks like this, change it.

Douglas Sacha / Getty Images

For many of us, our home's heating and cooling system is easy to forget about. 

Your HVAC (heating, ventilation and air conditioning) system operates in the background, actively works to make you feel comfortable and doesn't require much attention beyond changing the thermostat

When your HVAC system stops working, you definitely notice. Depending on whether you're faced with a small issue or require a full replacement, HVAC repairs could cost you thousands of dollars, all while you wait in a hot or cold house. 

How can you avoid that disruption? 

It's not a guarantee that nothing will ever go wrong, but regular and properly performed maintenance can make all the difference. If you can stay on top of your HVAC system, you can prevent outages, cut costs and even maintain cleaner air. 

But much of that maintenance isn't a realistic job for the typical person and will require some input from a professional. Here's what to know about what you should do to maintain your system -- and when to call in the pros.

Why regular HVAC maintenance matters

Why maintain your HVAC system? The easiest answer is the simplest one: Because the manufacturer says you need to. 

"Maintenance is required to maintain a manufacturer warranty," said Chris Morin, a regional sales manager for Mitsubishi Electric Trane HVAC US. "It's in everybody's policy. So that's probably the No. 1 thing." 

Manufacturers place an emphasis on regular upkeep because their systems simply won't operate as intended without it. From replacement filters to coolant, your HVAC system is like your car in that it needs regular attention. Without it, your system could be struggling without you even realizing. 

"The other side of it is comfort and energy savings," Morin said. "The system will operate…but the longer you go without maintenance, the more it's going to cost you in operating costs. And by the time somebody's realized there's a comfort problem, they either wasted a lot of money operating or there's already a failure." 

Pinpointing wasted money from HVAC is critical at a time when people are seeing increasing energy costs. Morin said METUS polled its customers last year and found that 46% said they were spending more or much more on energy costs to cool their homes last summer, even though last summer was cooler than the one before. And while energy costs are certainly an element of that increase, Morin said more people might be hurting themselves by falling behind on maintenance than they think. 

"The highest-efficiency systems are typically variable speed units," he said. "If you don't do maintenance, they tend to ramp up and use more energy to deliver the same amount of BTUs. So you might not notice a comfort problem, but your bills continue to go up, whereas with older systems, you just start getting that comfort problem right away. Your bill doesn't go up, but you don't have comfort." 

Just as is the case with your car, proper HVAC maintenance can also drastically impact longevity of a unit. Depending on your particular circumstances, a lack of maintenance can either directly cause damage or simply allow for conditions that worsen over time. Without knowing what's in your system, you can also allow yourself to be exposed to mold spores and other irritants in the air. 

"Nuisance calls or (issues) where you could be at the point where you're weighing whether you repair or replace the system are caught much earlier when you do annual maintenance," Morin said. "Refrigerant leaks that impact compressor operation, mold that happens with water and dark places, a lot of that happens because of a lack of maintenance, changing filters and not clearing drains. That stuff starts to compound over the years." 

When to call a professional for HVAC maintenance

Does a desire to better maintain your HVAC system mean you should run out and start working on it yourself? Not necessarily. 

Fortunately, there are some basic maintenance items that anyone can do in their own home. Changing the filter, for instance, is an extremely important task that virtually anyone can do and can make a major impact on air quality. HVAC filters should usually be changed every 30 days or so. A clean filter allows more air to pass through, which makes the system heat and cool more efficiently. 

At the same time you're replacing your filters, take a look around to ensure condensation is draining properly, access doors are closed, thermostat batteries are full and everything else is in order. 

Similarly, make sure the area around HVAC units is kept clear from things like boxes, trees, bushes and other debris. This allows proper airflow and easy access. 

But beyond those basics, most people will want to call a professional. And in Morin's experience, many would rather err on the side of caution when it comes to their home's HVAC.

"I think there are people that just prefer to let the professional always handle it," he said. "There are some home services companies that might include that with plumbing maintenance and other things. And then there's the more tech savvy people, or people that are hands-on with their home, that maybe they might go a little too far themselves and they might get themselves in a little trouble." 

Often, manufacturers will make it clear in their user manuals whether certain tasks should be performed by a professional. "We have a pretty clear operation manual for all of our systems that states what a homeowner should and can do," Morin said. "And then there's recommendations like, 'If you see a certain thing, call a professional.' Maybe you need EPA certification to verify refrigerant levels or that sort of thing." 

One tricky variable comes when you don't own the home. Renters likely aren't responsible for maintaining HVAC systems -- aside from perhaps changing filters -- but should still keep an eye out for issues that could be incoming. Ultimately, they'll be the ones to deal with interruptions, so they should alert their landlords of any potential changes or issues. 

"Renters are always in a tough situation," Morin said. "If they're paying the electric bill, especially with a heat pump or an air conditioner, then you want to be more proactive about making sure maintenance is done. If it's not on (their lease), it's not their responsibility to do it, and they might be able to get away with just making sure the filters are cleaned regularly like they should be, depending on the type of system you have." 

A person changing an air filter in a furnace, with a water heater in the background.

Changing your air filter regularly is a vital part of making sure your HVAC system is running efficiently.

Marvin Samuel Tolentino Pineda / iStock / Getty Images

How to maintain your HVAC system

HVAC systems can be decades old, come in a range of styles and manufacturers, and are set up very differently from home to home. That means there's no one set guide or method for maintaining a system. 

But in addition to replacing filters, Morin does have one overarching tip for just about anyone: "People should be more proactive with every system."  

Maintaining a gas furnace

Under the correct circumstances, maintaining a gas furnace shouldn't be too costly or difficult. As is the case with any other system, regular annual maintenance calls should be performed so that technicians can ensure everything is working correctly. 

That proactivity is actually a bit more important for gas furnaces because of the way they heat. Gas doesn't produce soot, which can lead people to assume it's working fine even if they haven't performed regular maintenance. And, as is the case with any gas-related item, it's critical to ensure gas isn't leaking out where it's not supposed to be. 

In general, catching any issue early is critical with a gas furnace, because something can start to go wrong without showing itself to a novice. 

"And then all of these other issues start to creep in," Morin said. 

Maintaining an air conditioner

Because of the condensation and moisture involved with air conditioners, cleaning and replacing filters is extremely important to their operation. 

In general, air conditioning is a resilient system that will keep working even when it's not operating at its most efficient.

"People might see that it's blowing cold air from the air conditioner, but the longer you go without maintenance, the more it's going to cost you in operating costs," he said. "And by the time someone realizes there's a comfort problem, they probably wasted a lot of money operating or there's already a failure." 

Morin's biggest recommendation is to schedule air conditioning maintenance outside of peak times during the summer. By scheduling a visit by mid-April before most parts of the country get hot, you can both lower costs and avoid waiting for a tech to find time for your unit during hot summer months when everyone is experiencing the same issue. 

"A good contractor tends to reach out to their customer base before it's really warm out, so they're able to schedule this at a time that makes sense before it gets to the heat wave," Morin said. "If a system breaks and they haven't maintained it and it's really hot, everybody's calling them. So the ability to respond to everybody's not there. By doing maintenance early, it helps the contractor and the customer kind of level their labor requirements and keeps it affordable at a time when they're not really busy for the customer." 

Maintaining a heat pump

Just like any other kind of unit, Morin recommends heat pump maintenance from a professional at least once per year. 

Most times, heat pump maintenance is largely preventative and is more about the efficiency of the unit and potential cost savings than about ensuring safety. In general, heat pumps have lifespans of up to 20 years and usually come with a warranty of at least 10 years. 

But just because they're functioning doesn't mean they don't need any maintenance, so be sure to schedule them regularly. And like the air conditioning advice, Morin suggests scheduling heat pump maintenance in the spring after the coldest part of the season is over. That will help you miss the rush and maybe save a few dollars. 

For those who are considering switching HVAC methods, a heat pump may be a good option because its cleaner operation means there are currently tax incentives and utility rebates available for those who switch

Maintaining oil or electric furnaces

To a typical resident, there won't be much of a difference between maintaining oil or electric furnaces when compared with traditional gas furnaces. 

Internally, these units function very differently. But unless you're an expert who's going to be working on them in an informed way, you likely won't encounter anything specific to these units that will change how you personally maintain them. 

As is the case for any HVAC systems, you'll want to stay on top of changing filters, paying attention to changes and keeping their areas clean. And just like everything else, it's recommended to schedule annual maintenance to ensure nothing is going wrong behind the scenes. 

What does the future of HVAC look like? 

Some of the older HVAC methods -- like boilers or oil furnaces -- are in the middle of a long process of phasing out in favor of more clean and efficient technology. That means, over the next several years, Morin expects to see a change in the HVAC norm in residential spaces. 

So what's the right solution for someone buying a new system? The answer can be frustrating, but it's the only accurate one: It depends. 

"When you talk about selecting a system, the number one thing is that it's sized correctly," Morin said. "There's a process for sizing. Even when you replace a system, things change in the house and they really should size the system based on the house that you have today. Then, after that, you start addressing the needs of the occupants."

Those needs could focus on air quality for a family with kids with asthma, or a focus on the comfort of one room in particular for people who work from home, he said.

But no matter what kind of system you have or will have, it deserves your attention regularly.