How do I find out how old my furnace or AC is?
To find a furnace or AC's age, look on the data plate inside the cabinet or on the outdoor unit for a printed manufacture date. With only a serial number, check the install sticker, the city permit and your records. A furnace replacement with us runs $4,500–$9,500.
Key points
- Look for a printed manufacture date on the data plate before anything else.
- The plate is inside the furnace cabinet and on the cabinet of the outdoor AC or heat pump unit.
- No date on the plate? Check for an installer's sticker, the building permit and the paperwork from the home purchase.
- Brands hide the date in the serial number differently, so ask the manufacturer or us instead of using a chart.
- Age decides repair or replace, whether the AC uses R-22, and whether a warranty is still in play.
The fastest way to date a furnace or AC is the data plate, also called the rating plate, which many manufacturers print with a month and year of manufacture. If the plate lists only a model and serial number, the date is coded into the serial and every brand codes it differently, so the dependable fallbacks are the install sticker, the city permit and your own records. Bring a flashlight and your phone.
Where is the data plate on a furnace?
The rating plate is a label inside the furnace cabinet. Manufacturer installation manuals send you to the "rating plate" for the model number and ratings, and it typically sits on the inside wall of the blower compartment or near the burners.
- Turn the furnace switch off (it looks like a light switch on or near the furnace).
- Open the lower door the normal way. Nothing needs removing. Most doors lift off or open on a quarter-turn knob.
- Photograph the label with your phone flash on. Get the model number, serial number and any date printed on it.
- Put the door back until it seats against its switch. The furnace won't run without it.
Don't touch wiring or the burner area. The model and serial number are enough to work from.
Where is the data plate on an outdoor AC or heat pump?
Look for a metal or foil label on the side of the outdoor cabinet, often near the panel where the electrical power enters. It lists the model number, serial number, electrical ratings and refrigerant type. Brush off leaves and dirt and photograph it. If a service sticker is on top of the plate, don't scrape off safety labels. The indoor coil or air handler has its own plate, and its age can differ from the outdoor unit's.
Why can't you trust serial number decoder charts?
A serial number is a factory tracking code first and a date second. The date sits in different positions by brand, some brands use a week and a year, others a month and a year, and some use letters. The same brand changes its format over the years, and several brands have changed more than once.
That is why online decoder charts disagree with each other, and why a rule that works for one brand gives a wrong decade on another. Some formats use a single digit or two digits for the year, so the same code can point to more than one decade and needs sense-checking against the house. A furnace in a house built in 2005 can't date from 1985.
So the order we recommend:
- Printed manufacture date. Look on the data plate for a field labeled something like "Date of Manufacture" or "Mfg. Date." Many plates show one. It's the answer.
- Install sticker. Installers often leave a service or installation sticker on the furnace door, the cabinet or near the thermostat wiring, with the company name and the install date. It tells you when the system went in, which can be later than when it was built.
- Permits. Furnace and AC replacements usually need a mechanical permit. Your city or county building department can look up permits by address, and the permit date is close to the install date.
- Homeowner records. Check the home-purchase paperwork and inspection report, past invoices, a warranty registration email, and any binder the previous owner left. Ask the previous owner or the installer's company if you can find a name.
- Manufacturer support. Give them the model and serial number. They're the source for their own format.
- Ask us. Read the plate to us over the phone, or have a technician confirm the date at a visit; a service call is a $79 trip charge, waived when you approve the repair.
Why does your furnace's age matter?
Repair or replace. Age is the first thing we weigh with the repair quote. We usually repair a young furnace with one failed part, and we usually replace an old one that needs a major part. Our price ranges are $4,500–$9,500 for a furnace replacement and $5,200–$9,800 for a central AC replacement. For typical life spans, see how long a furnace lasts in Minnesota and how long an AC lasts in Minnesota. For pricing, see furnace replacement cost and AC replacement cost.
R-22 on older ACs. R-22 production and import ended on January 1, 2020. An older AC built for it can only be recharged with reclaimed or stockpiled R-22, which is expensive. A national guide, HomeGuide, puts a typical R-22 recharge at $180–$600. The plate lists the refrigerant, so check it. Our R-22 phase-out guide covers the options.
Warranty. Many manufacturers want the equipment registered online within a set window after install for the longer parts warranty. Terms change by brand and year, so check the manufacturer's current terms. The serial number and install date are what a warranty claim starts from. If you moved into a house with the equipment already installed, the registration status may be unknown, and that's worth finding out before something fails.
Efficiency and parts. An older furnace may be an 80% AFUE model and a very old AC may be well below current efficiency standards. Parts for discontinued models can get hard to find.
What should you do once you know the age?
Once you have the model, serial and any printed date, you can decide what to do:
- Under a few years old: register it if you haven't, and keep the paperwork with the plate photo.
- Mid-life: have it maintained. Our maintenance tune-ups start at $129 for a furnace or an AC, and $219 for both.
- Old, or on R-22: get a written replacement quote now instead of waiting for a January no-heat call.
Read us the model and serial numbers when you call 612-429-3465, or see furnace repair in Minneapolis if the furnace is acting up already.
Common questions about heating
Where is the serial number on a furnace or AC?
On a furnace it is on the rating plate, a label inside the cabinet on the wall of the blower compartment or near the burners. On an outdoor AC or heat pump it is a metal label on the side of the cabinet, often near the electrical access panel. Photograph it instead of reaching into the cabinet, and don't scrape off safety labels.
Does the permit date tell me when my furnace was installed?
It is close. The city issues the permit before work starts, so it is dated a little ahead of install day, but near enough to date the system. Your city or county building department can look permits up by address, and the permit record often names the contractor too, which helps if you need the install paperwork.
Can my furnace and AC be different ages?
Yes. A furnace and an AC are often installed years apart, and the indoor coil or air handler carries its own plate that can show a different age from the outdoor unit. Read each plate on its own and write the dates down together, because repair-or-replace advice depends on which piece is oldest.
Is the date on the data plate the date my furnace was installed?
No. The plate shows when the factory built the unit. The install usually came months later, and sometimes years later if the equipment sat in a warehouse. The install sticker, the permit and your purchase paperwork give the install date, and the build date gets you within a year or two.
Sources
- HomeGuide: AC refrigerant recharge costs homeguide.com