Getting Your HVAC System Ready for Winter: An Owner’s Manual

Most homes have one system that runs quietly for months and only gets noticed when it stops. In a lot of the homes I manage, that’s the heating. It sits idle all summer, and then one cold evening in November someone turns up the thermostat and waits for warm air that doesn’t come.

Getting ready for winter isn’t complicated. It comes down to about an hour of owner-level checks and one professional visit, done early in the fall before technicians’ calendars fill up. This is how I approach winter HVAC maintenance, whether it’s a primary residence or a property that sits empty for part of the season.

Start by Knowing What You Have

Winter prep looks a little different depending on the system in your home, so start by identifying which one you’re working with. If you’re not sure, the label on the indoor equipment or your last service invoice will tell you.

• Forced-air furnace. Heats air using gas, propane or electricity and pushes it through ducts. Gas furnaces need an annual check of combustion and venting.

• Heat pump. An outdoor unit that moves heat into the house in winter and out of it in summer. Very common in California and in newer builds. The outdoor unit needs attention before the season.

• Boiler or radiant heat. Heats water that circulates through radiators or tubing in the floor. There’s no air filter to change, but pressure, valves and the boiler itself need a professional check.

• Ductless mini-split. A heat pump with wall-mounted indoor units, each with its own washable filter.
  

Many homes, especially larger properties, have more than one. A main house on a heat pump with a guest house on a mini-split is a common setup, and each system gets its own check. If any of these terms are new to you, our Home Decoder covers the basics.

The Owner’s Checklist: About an Hour, Once a Year

1. Replace or clean the filter. This is the single most useful thing you can do. A clogged filter restricts airflow, makes the system work harder and sends more dust back into your rooms. How often it needs changing depends on the filter and the household: thin filters need replacing more often than thicker media filters, and pets, allergies or nearby construction all shorten the interval. Check it monthly through the heating season until you know your home’s rhythm, and write the filter size somewhere you’ll find it next time. How to Find and Change Your HVAC Filter
   

2. Test the heat before you need it. On a mild day in early fall, switch the thermostat to heat and set it a few degrees above room temperature. Warm air should arrive within a few minutes. A faint dusty smell the first time is normal as dust on the heating elements burns off, and it should fade within the hour. A smell that lingers is worth a call to your technician, and if you ever smell gas, leave the house and call your gas utility from outside.
   

3. Check the thermostat. Replace the batteries if it uses them, confirm the time and schedule are correct, and set a heating schedule that matches how you actually use the home. For smart thermostats, make sure it’s still connected and that alerts go to the right person.
   

4. Give the equipment room to breathe. Furnaces and air handlers often live in closets, garages and utility rooms that slowly become storage. Move boxes, paint and anything flammable away from the unit, and keep a clear path for service. Your owner’s manual lists the clearance your specific unit needs. Outside, clear leaves and debris from around the heat pump and trim back plants so air can move freely around it.
   

5. Walk the vents and returns. Open the supply registers and make sure rugs, furniture and drapes aren’t covering vents or return grilles. Closing vents in unused rooms saves less than people expect and can make some systems work harder.
   

6. Test your carbon monoxide alarms. Any home with a gas appliance, a fireplace or an attached garage should have working CO alarms, and in California they’re required. Press the test button, replace batteries, and check the date on the back: alarms have a limited lifespan and the manufacturer lists when to replace them. It takes two minutes, and it’s the one item on this list I never skip.
   

7. Look at the condensate line and drain pan. High-efficiency furnaces and heat pumps produce water that drains away through a small line. Check that the pan isn’t holding water or showing rust, and that the line isn’t kinked or disconnected. Anything that looks off goes on the list for your technician.
   

One more thing worth adding to your routine: heating dries out indoor air. The EPA recommends keeping indoor humidity between 30 and 50 percent, and an inexpensive hygrometer will tell you where you are. If you have a whole-home humidifier, replace its pad at the start of the season. There’s more on this in our post on indoor air quality.

What Your Fall Tune-Up Should Include

The owner checklist covers what you can see. A professional visit covers the rest. I book tune-ups in September or early October, because once the first cold snap arrives, most HVAC companies are busy with repair calls and routine maintenance gets pushed back.

A thorough fall visit usually includes:

• Inspection of the burner, flame and heat exchanger on gas systems

• A check of the venting and flue, so exhaust leaves the house as it should

• Testing of electrical connections, controls and safety switches

• Cleaning and checking the blower and fan

• For heat pumps: refrigerant level, defrost cycle and the outdoor coil

• Clearing the condensate drain

• Confirming the thermostat is reading and responding correctly
  

Before the technician leaves, ask:

• What did you find, and is there anything I should keep an eye on?

• How old is the system, and what’s its realistic remaining life?

• Is there anything you’d fix now rather than wait on?

• Can you send me the report in writing?

  
  

Keep that written report. Over a few years, those reports become the most useful record you have when it’s time to decide between repairing and replacing. Our Vendor Template makes it easy to track who came, what they did and what’s next, and The Hidden Cost of Deferred Maintenance explains why small items are worth handling while they’re still small.

Second Homes and Empty Properties

A house that sits empty for weeks at a time needs its own plan. Nobody is there to notice the heat has stopped, so small issues have more time to become bigger ones. A few simple decisions made now take care of most of it.

• Keep the heat on at a sensible minimum. Don’t switch it off. In colder climates, the American Red Cross recommends keeping the thermostat no lower than 55°F while you’re away to protect your pipes. Even in a mild California winter, keeping the house tempered helps with moisture and protects finishes, wood and artwork.
  

• Add remote monitoring. A smart thermostat that sends an alert when the temperature moves out of range is one of the most useful tools for a second home. Add water leak sensors near the water heater and HVAC equipment at the same time.
  

• Decide who checks in, and how often. Name one person, whether that’s a caretaker, a neighbor or a property manager, with a key and a short checklist: is the heat running, any unusual smells or sounds, any water around the equipment. Ask them to check after storms and cold snaps too.
  

• Schedule service around your calendar. Book the tune-up for a week you’ll be there, or arrange access in advance so it doesn’t slide to spring.
  

When to Call Someone Now

Not everything can wait for the annual visit. Call a technician if you notice:

• The system turning on and off in short bursts

• Rooms that are noticeably colder than they used to be

• New sounds such as banging, grinding or squealing

• A burning or electrical smell that doesn’t fade

• On a gas furnace with a visible flame, a yellow or flickering flame instead of a steady blue one

• Energy bills climbing without any change in how you use the home
  

And if a carbon monoxide alarm sounds, get everyone outside first, then call for help. Don’t try to find the cause yourself.

Keep the Records in One Place

The best-run homes I work with have one thing in common: someone knows where the information is. For your heating system, that means the make and model, install date, filter size, service dates and reports, and your technician’s contact details. Keep them together in a binder, a shared folder or a note on your phone, and next year’s winter prep takes half the time.