How Old Is My Furnace or AC?
The date is encoded in your furnace or AC's serial number, on the rating plate. Pick your brand and enter the serial, and we'll decode it — Goodman, Carrier, Lennox, Trane, York and their related brands are all covered.
Where’s the serial number?↓
- On the outdoor condenser (AC or heat pump): a metal rating plate on the side of the cabinet, near the refrigerant line connections.
- On the furnace or air handler: inside the front access panel, on the side wall of the blower compartment — often on a sticker, sometimes stamped into the sheet metal.
- On a packaged rooftop or through-the-wall unit: on the exterior of the cabinet near the electrical connections.
- Many units also print a plain "Mfg Date" or "Date of Manufacture" line on the same plate — if you see one, trust it over the serial.
Not the model number, which describes the equipment (tonnage, efficiency, cabinet) but not when it was built. Only the serial carries the date, and on Goodman, Carrier and Lennox it is in the first few characters.
- Goodman, Amana and Daikin share one format: the first four digits of the serial are the year, then the month. 2205… is May 2022. In use since the late 1990s.
- Carrier, Bryant and Payne put the week first, then the year: 3216… is week 32 of 2016. All three are built by Carrier.
- Lennox uses a two-digit plant code, then the two-digit year, then a letter for the month (A-M, skipping I): 1606B… is February 2006.
- Trane and American Standard units built since 2010 put the two-digit year first, then the week: 1204… is week 4 of 2012. Units from 2002-2009 use a single year digit, then the week.
- York, Luxaire and Coleman have shared one format since 2004: characters 2 and 4 together are the year, and character 3 is a letter for the month. N0D6653823 is April 2006.
- Rheem/Ruud HVAC, Nordyne, Heil/Tempstar, and pre-2002 Trane / pre-2004 York units use codes this tool does not read yet — use the printed "Mfg Date" on the rating plate.
Is something wrong with it, or are you just checking?
The age means different things depending on the answer. Pick one and we'll show you only what applies.
What the age actually means for a furnace or AC
A furnace typically lasts 15 to 20 years, and a central AC or heat pump 10 to 15.
What does the age mean if something is wrong?
Age changes the economics; symptoms tell you what to diagnose. Neither alone determines the answer.
Usually worth diagnosing/repairing
Replacement becomes more worth considering when
A screening tool, not a decision engine: multiply the repair quote by the unit's age in years. Past roughly $5,000, replacement is worth taking seriously. A cracked heat exchanger or a failed compressor on an older unit tends to tip this calculation toward replacement quickly, but even those are worth confirming against the unit's actual age and warranty status rather than treated as an automatic verdict.
Still not sure about the furnace? See the full furnace repair-or-replace guide →
For the AC or heat pump, there’s no single repair-or-replace guide yet — start with what the specific repair costs: AC capacitor replacement cost (the cheap, common one) or AC compressor replacement cost (the one that usually forces the decision).
Where a furnace or AC sits in its lifespan
15–25 years
Typical range
~20 years
Planning average
Early life (Years 1-5)
Ignitors, flame sensors, run capacitors and contactors are examples of cheap wear parts that can fail — not a sign the system is failing.
Mid-life (Years 6-10)
Blower and condenser-fan motors, control boards, and the first refrigerant leaks on air conditioners are examples of repairs that come up. Still repairable, but the bills start.
Planning window (Years 10-15)
Compressor failure becomes more common on ACs and heat pumps, and repair history starts to matter more than the age number alone. On furnaces, a heat exchanger problem becomes a real possibility — see the notes below on how that decision actually gets made.
Beyond typical range (Years 15+)
Past typical air-conditioner life and into the range where a furnace replacement is worth planning for. R-22 systems are increasingly expensive to keep running on refrigerant alone.
*Actual lifespan depends on usage, maintenance and quality. Well-maintained appliances often exceed these averages.
*A gas furnace typically runs 15 to 20 years (25+ well-maintained); a central AC or heat pump 10 to 15. Correct sizing, install quality and whether the filter was changed on schedule matter more than the brand.
If there’s a problem, age changes the repair economics; if it’s working, maintenance is the next step.
A gas furnace typically lasts 15 to 20 years and a central air conditioner or heat pump 10 to 15 — on a younger system, isolated wear-part faults (an ignitor, a run capacitor) are usually inexpensive next to a new system, so repairing is the straightforward call.
As a system ages, compressor failure on an AC or heat pump and heat-exchanger concerns on a furnace become more relevant to the repair-vs-replace decision — though even a heat-exchanger flag is worth confirming against the unit's actual age and warranty status rather than treated as an automatic verdict (see the facts below).
The furnace and AC sides diverge here: furnace repairs stay comparatively worth paying for later, similar to a dryer, while a failed compressor on an AC or heat pump past about 10 years is one of the stronger signals that replacing the outdoor unit is the better spend. Age, repair history and the specific failure still matter more than any single number.
Things worth knowing about your system
The age is on the outdoor unit, not the thermostat
A new smart thermostat tells you nothing about the system behind it. The date you want is on the rating plate of the outdoor condenser, or inside the furnace cabinet — the boxes that actually wear out.
A cracked heat exchanger is a safety issue — confirm before deciding
The heat exchanger is the steel wall between the burner flame and the air you breathe. Once it cracks, the furnace can leak carbon monoxide into the house, so it always warrants professional evaluation and should not be run until checked. Whether the right fix is repairing the heat exchanger itself or replacing the furnace depends mainly on the unit's age and warranty coverage — a technician's "replace it" recommendation on a younger, warrantied furnace is worth a second opinion, not just taken on faith.
R-22 is the deadline hiding in an older AC
Air conditioners installed before roughly 2010 use R-22 refrigerant, which was banned from production in 2020. A system that develops a leak can still be topped up in theory, but reclaimed R-22 now costs several times what it did, which quietly turns a small repair into a replace-or-not decision.
R-410A systems are not the next R-22 — yours is still fine to service
Most air conditioners installed since the mid-2000s run on R-410A, and as of January 2026 the EPA has stopped allowing R-410A in newly manufactured equipment (new installs now use R-454B or R-32 instead). That rule affects new equipment only — it does not ban R-410A itself, and existing R-410A systems remain fully legal to recharge and service. If a technician suggests otherwise, get a second opinion before treating a routine repair as a forced replacement.
The install matters as much as the brand
An oversized unit short-cycles and wears out early; undersized ductwork strains the blower. A mid-tier system installed well outlasts a premium one installed badly, which is why two identical units in the same neighbourhood can fail a decade apart.
Common questions
How old is my furnace, AC or heat pump?
Find the serial number on the rating plate — on the side of the outdoor condenser, or inside the furnace access panel — and enter it above. Goodman, Amana and Daikin encode the year then the month in the first four digits; Carrier, Bryant and Payne use the week then the year; Lennox uses a plant code, the year, then a letter for the month.
How do I do an HVAC serial number lookup?
Read the manufacture date straight out of the serial number on the rating plate — there is no database to search. For a Goodman, Amana or Daikin unit the first two digits are the year and the next two the month. Carrier, Bryant and Payne put the week first, then the year. Lennox uses a plant code, then the year, then a letter for the month. Enter the serial in the calculator above and it does the reading for you.
Where is the serial number on an HVAC unit?
On the metal rating plate. For an AC or heat pump it is on the side of the outdoor cabinet near the refrigerant connections. For a furnace or air handler it is inside the front panel, on the wall of the blower compartment. Do not use the model number — only the serial carries the date.
How long does an HVAC system last?
A gas furnace typically lasts 15 to 20 years, and a central air conditioner or heat pump 10 to 15. Install quality, correct sizing and whether the filter was changed on schedule matter more than the brand.
Can I tell the age from the model number?
No. The model number describes the equipment — its capacity and efficiency — not when it was built. The manufacture date is only in the serial number. On Goodman, Carrier and Lennox units it sits in the first few characters of the serial.
How do I read a Trane serial number for the age?
Trane and American Standard units built since 2010 start with a two-digit year, then a two-digit week — a serial beginning 1204 is week 4 of 2012. Units from 2002 to 2009 use a single year digit, then the week. Enter the serial above and the calculator reads the year. Pre-2002 Trane serials start with a letter and use a code this tool does not read — use the printed manufacture date for those.
How do I read a York, Luxaire or Coleman serial number?
York, Luxaire and Coleman have used one format since 2004: a letter, a digit, a letter, a digit, then six digits. Characters 2 and 4 together are the year (N0D6653823 has 0 and 6, so 2006), and character 3 is a letter for the month (D is April). Enter the serial above and the calculator does it for you. Units older than 2004 used a letter code that is not readable here.
The decoder above reads all of these automatically. This is the reference if you want to work it out yourself, or check its answer — each maker puts the date in a different place, and the unit almost never has a plain printed date.
How old is my Goodman, Amana or Daikin furnace, AC or heat pump?
This is the Goodman serial number lookup — and the same code reads Amana and Daikin HVAC. To find a Goodman's age by serial number, take the first four digits: two for the year, then two for the month.
- Covers:
- Goodman, Amana, Daikin.
- What the serial looks like:
- 10 digits, starting with the date — 2 digits for the year, then 2 for the month (e.g. 2205… = May 2022)
- Reading the year:
- Goodman states the year in full in the first two digits, so there is no decade guesswork.
- Where the serial number is:
- On the metal rating plate: condensers and heat pumps — on the side or back of the outdoor unit; furnaces and air handlers — inside the front panel, on the side wall.
- Don’t use:
- Not the model number (starts with letters, e.g. GSXC180361, AMVT80805). The serial is the all-digit code, usually printed just below the model.
- Worked example:
2205123456 → May 2022
How old is my Carrier, Bryant or Payne AC, furnace or heat pump?
For a Carrier serial number lookup — which also covers Bryant and Payne — read the first four digits: two for the week of the year, then two for the year. The week comes first, which trips people up.
- Covers:
- Carrier, Bryant, Payne.
- What the serial looks like:
- Starts with 4 digits — 2 for the week of the year, then 2 for the year (e.g. 3216… = week 32 of 2016)
- Reading the year:
- The year is stated in full (digits 3-4), so there is no decade guesswork — but the week comes first, which is the reverse of most brands.
- Where the serial number is:
- Condensers and heat pumps — on a plate on the side of the outdoor unit; furnaces and fan coils — inside the access panel on the side wall.
- Don’t use:
- Not the model number (letters and digits mixed, e.g. 24ANB136A003). The serial is the separate code that begins with four digits.
- Worked example:
3216E54321 → August 2016
How old is my Lennox furnace, AC or heat pump?
To tell a Lennox unit's age by its serial number, read digits 3-4 (the year) and character 5 (a letter for the month, A-M skipping I). The first two digits are just the plant code.
- What the serial looks like:
- Digits 3-4 are the year, character 5 is a letter for the month (e.g. 1606B… = February 2006)
- Reading the year:
- Lennox states the year in full in digits 3-4, so there is no decade guesswork.
- Where the serial number is:
- On the rating plate: condensers and heat pumps — on the side of the outdoor unit; furnaces and air handlers — inside the front door on the side wall.
- Don’t use:
- Not the model number (has dashes and mixes letters and digits, e.g. XC25-036-230, SLP99UH110XV60C).
- Worked example:
1606B13871 → February 2006
How old is my Trane or American Standard AC, furnace or heat pump?
For a Trane serial number lookup — which also covers American Standard — read the first digits: units built since 2010 put the 2-digit year first, then the 2-digit week (1204… = week 4 of 2012). Units from 2002-2009 use a single year digit, then the week.
- Covers:
- Trane, American Standard.
- What the serial looks like:
- Starts with digits. Units from 2010 on: 2 digits for the year, then 2 for the week (e.g. 1204… = week 4 of 2012). Units from 2002-2009: 1 digit for the year, then 2 for the week.
- Reading the year:
- The year is stated in full. Trane changed the format in 2010: before that the year was a single digit (2002-2009). If your unit is clearly pre-2010 and the reading looks off, the first digit alone is the year.
- Where the serial number is:
- Condensers and heat pumps — on the data plate on the side of the outdoor unit; furnaces and air handlers — inside the front door, on the side wall of the blower section.
- Don’t use:
- Not the model number (starts with a letter or a digit-then-letters, e.g. 4TWR4048G1000A, TUD100C948K0). The datable serial is the one that starts with plain digits.
- Worked example:
1204ABCDEF → January 2012
How old is my York, Luxaire or Coleman furnace, AC or heat pump?
York, Luxaire and Coleman have shared one serial format since 2004: characters 2 and 4 together are the year (N0D6653823 → 0 and 6 → 2006), and character 3 is a letter for the month.
- Covers:
- York, Luxaire, Coleman.
- What the serial looks like:
- 10 characters: a letter, a digit, a letter, a digit, then 6 digits (e.g. N0D6653823). The 2nd and 4th characters together are the year; the 3rd is a letter for the month.
- Reading the year:
- The year is stated in full (characters 2 and 4). York, Luxaire and Coleman have used this identical format since 2004; older units use a letter code this tool does not read.
- Where the serial number is:
- Condensers and heat pumps — on the rating plate on the side of the outdoor cabinet; furnaces and air handlers — inside the front panel of the blower compartment.
- Don’t use:
- Not the model number (longer, all letters and digits mixed, e.g. YCJF36S41S1, TM9V080B12MP11).
- Worked example:
N0D6653823 → April 2006
Rheem, Ruud, Nordyne and Heil / Tempstar: these changed their serial date codes several times and some eras can’t be read without guessing, so the decoder doesn’t attempt them yet. Older pre-2002 Trane and pre-2004 York/Luxaire/Coleman units (letter date codes) are the same. Use the “Mfg Date” line printed on the rating plate, or enter the year directly — the rest of the page still works.
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The Furnace Series
- 1How Long Does a Furnace Last?See the typical lifespan, what changes as a furnace ages, and when to start planning ahead.
- 2Should You Repair or Replace Your Furnace?Use age, repair cost, and the type of failure to decide whether fixing it still makes sense.
- 3How Much Does It Cost to Replace a Furnace?See typical installed costs, what drives the price, and what to expect before getting quotes.
The Air Conditioning Series
- 1How Long Does an AC Last?The failure timeline by age, what shortens it, and when age alone says replace.
- 2How Much Does an AC Capacitor Replacement Cost?The cheapest and most common AC repair — $80 to $400, and why a $15 part costs that much.
- 3How Much Does an AC Compressor Cost to Replace?Cost by system size, warranty vs not, and when replacing the whole system is the better call.