How old is your AC? Read it off the serial number.

Finding the number

Where the serial number is

Look on the outdoor unit — the condenser or heat pump outside, not the furnace or air handler indoors. The serial number is printed on its rating plate, also called the nameplate [6]. American Standard, for example, puts the label at the top right-rear of its outdoor units [14].

The same plate usually lists the refrigerant the system uses, which matters if it is older [21]. A photo of the plate is the easiest way to keep the numbers to hand.

How old is old?

There is no expiry date, but there is a 10-year cue

ENERGY STAR and the U.S. Department of Energy both suggest calling a contractor to consider replacement when a heat pump or air conditioner is more than 10 years old [16] [18], or when it is not keeping the house comfortable [17].

That is a cue to get it looked at, not a lifespan. For comparison, in its federal buying guidance the Department of Energy's Federal Energy Management Program works out lifetime costs assuming an average central air conditioner life of 18 years in hot, humid Southeast states, 24 years in northern states and 25 years in hot, dry Southwest states [19]. Those are planning assumptions for cost comparisons, not a promise about any one unit.

Repair or replace

The signs ENERGY STAR lists

Source for the list: ENERGY STAR [16]. Some of those symptoms can come from ducts or insulation rather than the equipment, so before paying for a new system, ENERGY STAR advises dealing with big air leaks and the duct system first — and getting the new equipment installed properly, because improper installation can cut a system's efficiency by up to 30 percent [17].

Older systems

If it was made before 2010: R-22

R-22 (HCFC-22) was the most common refrigerant in home air conditioners and heat pumps for decades[20]. From 1 January 2010 it stopped being used as a factory-installed refrigerant[13], and U.S. production and import ended on 1 January 2020 [21].

You do not have to replace an R-22 system. EPA does not require it, and existing systems can still be serviced with recycled, reclaimed or previously produced R-22 [20]. Do not let anyone top it up with “R-22a”: EPA says that product is a flammable hydrocarbon blend and not an acceptable substitute [21].

What we can read

Brands we decode, and brands we don't

• CarrierWeek, then year, then a factory letter (e.g. 0106E… = week 1 of 2006). We only date units from 2006 on: the earliest year the manufacturer's documents we read show this format in use. [6][8]
• BryantWeek, then year, then a factory letter (e.g. 0106E… = week 1 of 2006). We only date units from 2006 on: the earliest year the manufacturer's documents we read show this format in use. [9][6]
• GoodmanFirst four digits are the year and month (e.g. 2002… = February 2020). We only date units from 2020 on: the earliest year the manufacturer's documents we read show this format in use. [1][4]
• AmanaFirst four digits are the year and month (e.g. 1306… = June 2013). We only date units from 2013 on: the earliest year the manufacturer's documents we read show this format in use. [2][3]
• DaikinFirst four digits are the year and month (e.g. 2112… = December 2021). We only date units from 2021 on: the earliest year the manufacturer's documents we read show this format in use. [4][5]
• LennoxFactory code, then year, then a month letter (e.g. 5821C… = March 2021; Lennox publishes month letters A–C only, so later letters give the year alone). We only date units from 2017 on: the earliest year the manufacturer's documents we read show this format in use. [10][11][12]
• TraneNot decoded. Trane says the serial number records the manufacture date, but we could not find a Trane guide to reading it on home systems, so we will not guess. A Trane dealer or technician can confirm the date from the serial number. [13]
• American StandardNot decoded. American Standard explains where its serial number is, but we could not find its own guide to reading a date from it, so we will not guess. A dealer or technician can confirm the date from the serial number. [14]
• RheemNot decoded. Rheem describes its date code in one sentence but publishes no worked example, so we cannot check a reading against it yet. A technician can confirm the date from the rating plate. [15]
• RuudNot decoded. Ruud is made by Rheem, and Rheem publishes no worked example of its date code, so we cannot check a reading against it yet. A technician can confirm the date from the rating plate. [15]
• PayneNot decoded. We could not find this manufacturer's own published serial-number format, so we will not guess. A technician can read the manufacture date from the rating plate, or the manufacturer can look it up from the serial number.
• YorkNot decoded. We could not find this manufacturer's own published serial-number format, so we will not guess. A technician can read the manufacture date from the rating plate, or the manufacturer can look it up from the serial number.

What happens next

If you ask for quotes, this is the whole process

1. 01

   You describe the fault

   Four or five questions: what stopped working, how urgent it is, the kind of property, and your ZIP code. It costs nothing and you are not committing to anything.

2. 02

   Local companies get the request

   It goes to HVAC companies that cover your ZIP code and are taking work. Nobody pays to be sent a request, so you are not being routed to whoever bid highest.

3. 03

   They contact you

   A company that wants the job pays to open your contact details, then calls or emails you. Until one of them pays, nobody has your phone number — not even the companies the request was offered to.

What we are

Who is behind this page

Sources

Where every fact on this page comes from

Manufacturer documents, ENERGY STAR, the U.S. Department of Energy and EPA only. Each was read in full on the date shown. Where we read a manufacturer's document from a dealer's or distributor's copy, it says so under the entry. Those copies are sources [1], [2], [3], [8], [9]; both Amana documents and the Bryant manual were found only as such copies.

1. [1]

   Goodman Manufacturing Company, L.P.. Limited Warranty, models GSX13/GSX14/GSX16/GSZ14/GSZ16, Part No. PWGACHPTTYURA (06/2020)

   Goodman: "The first four digits of the serial number (YYMM) on the unit indicate the manufacture date"; example "2002" = February 2020.

   Read 2026-10-27 · Primary source · Dealer-hosted copy (budgetheating.com)

2. [2]

   Goodman Company, L.P. (Amana brand). Limited Warranty, models ASX13/ASZ13/ANX13/ANZ13, Part No. PWAACHPPH (© 2014-2015)

   Amana: same YYMM rule; example "1306" = June 2013.

   Read 2026-10-27 · Primary source · Distributor-hosted copy (Watsco / Gemaire); no manufacturer-domain copy of an Amana certificate was found

3. [3]

   Goodman Company, L.P. (Amana brand). Limited Warranty, models APC15H/APH16H/APH16M, Part No. PWAACHPCTYUR (© 2019)

   Amana: same YYMM rule; example "2002" = February 2020.

   Read 2026-10-27 · Primary source · Distributor-hosted copy (Watsco / Gemaire); no manufacturer-domain copy of an Amana certificate was found

4. [4]

   Daikin Manufacturing Company, L.P.. Limited Warranty, models DX13/DZ14, Part No. PWDACHPHTWZB (© 2021)

   Daikin (served from goodmanmfg.com): same YYMM rule; example "2112" = December 2021.

   Read 2026-10-27 · Primary source

5. [5]

   Daikin Comfort Technologies Manufacturing, L.P.. Limited Warranty, single-phase models DX3SE/DX4SE/DX5SE/DZ4SE/DZ5SE, Part No. PWDACHPTWSH

   Daikin (served from daikincomfort.com): same YYMM rule; example "2307" = July 2023.

   Read 2026-10-27 · Primary source

6. [6]

   Carrier Corporation. Residential Air Conditioners and Heat Pumps Using R-22 and Puron Refrigerant, Application Guideline and Service Manual, Catalog No. 24-25-2SM (04/08)

   Carrier "Serial Number Nomenclature": 01 06 E 00001 = week of manufacture, year of manufacture, manufacturing site (E = Collierville TN, X = Monterey Mexico), serial number. The manual covers units produced in 2006 and later.

   Read 2026-10-27 · Primary source · shareddocs.com (Carrier HVAC document library; ownership of the domain not independently verified)

7. [7]

   Carrier Corporation. 38AU Air Cooled Condensing Units, 60 Hz, Sizes 16-25, Installation, Start-Up and Service Instructions, Catalog No. 38AU-12SI (08/12) — a COMMERCIAL unit

   Context only, not used to decode: on this commercial Carrier unit, serial positions 1-2 = week of manufacture "(fiscal calander)", 3-4 = year ("12" = 2012), 5 = manufacturing location, 6-10 = sequence; typical serial 0512C12345. It is why we do not turn a Carrier week into a month.

   Read 2026-10-27 · Primary source · shareddocs.com (as above)

8. [8]

   Carrier. Residential Air Conditioners and Heat Pumps Using Puron Advance (R-454B), Application Guideline and Service Manual, Catalog No. ACHPR454-01SM (11/25)

   The same week / year / site / serial nomenclature (01 06 E 00001) in Carrier's current R-454B manual.

   Read 2026-10-27 · Primary source · Dealer-hosted copy (irp.cdn-website.com)

9. [9]

   Carrier (Bryant-branded manual: refers to Bryant thermostats and Bryant.HVACPartners.com). Residential Air Conditioners and Heat Pumps Using Puron Advance (R-454B) Refrigerant, Application Guideline and Service Manual, Catalog No. SMACHPR454-01 (11/25)

   Bryant: the same week / year / site / serial nomenclature (01 06 E 00001) as Carrier.

   Read 2026-10-27 · Primary source · Dealer-hosted copy (irp.cdn-website.com). No Bryant-branded document was found on a manufacturer domain.

10. [10]

    Lennox Industries Inc.. Unit Information, ML17XC1 Series Units, Corp. 100049 (June 22, 2023)

    Lennox "Typical Serial Number Identification": 58 21 C 05716 = location code (58 = Marshalltown IA, 19 = Saltillo MX), year code (21 = 2021), month code (A = January, B = February, C = March), 5- or 6-digit unique number.

    Read 2026-10-27 · Primary source

11. [11]

    Lennox Industries Inc.. Lennox Residential Communicating Systems Alert Code Guide (V2), 100017 (3/2023)

    Lennox: "Serial number format on unit name plate is PPYYMNNNNN (PP = Manufacturing Plant, YY and M represents the year and month made"; refers to units by serial prefix 5817F.

    Read 2026-10-27 · Primary source

12. [12]

    Lennox Industries Inc.. Engineering Handbook, model number identification (R-454B / R-32), 2503

    Lennox serial number: location code, year code (19 = 2019 through 23 = 2023), month code (A = January, B = February, C = March), 5- or 6-digit unique number. The published month table stops at C. Its printed example is "59 21 CO 05716" — a TWO-character month field ("CO") that this handbook does not explain, so serials with two letters there are not decoded.

    Read 2026-10-27 · Primary source

13. [13]

    Trane. Owner's Guide, Outdoor Units: Heat Pumps, Air Conditioners, 22-5213-WEB01

    Trane says the factory manufacture date "is verified by the Product serial number"; we found no Trane guide to reading it on residential units. Also: "Beginning on January 1, 2010, R-22 refrigerant will no longer be used as a manufacturer-installed refrigerant as required by federal regulation."

    Read 2026-10-27 · Primary source

14. [14]

    American Standard Heating & Air Conditioning (served from americanstandardair.com). Locating The Serial Numbers On Your New Products

    On an American Standard air conditioner or heat pump "the serial number label is located on the top, right-rear of the outdoor unit". The document explains where the number is, not how to read a date from it.

    Read 2026-10-27 · Primary source

15. [15]

    Rheem Manufacturing Company. What to Know Before Meeting with an HVAC Contractor

    Rheem states a rule ("The first two numbers after the letter in the middle or beginning of the serial number are the week of manufacture, and the third and fourth numbers are the year of manufacture") but gives no worked example, so we do not decode Rheem or Ruud yet.

    Read 2026-10-27 · Primary source

16. [16]

    ENERGY STAR (U.S. EPA / DOE). When is it time to replace?

    Signs it may be time to call a contractor: the heat pump or air conditioner is more than 10 years old; frequent repairs and rising energy bills; rooms too hot or too cold; humidity problems; a noisy system.

    Read 2026-10-27 · Primary source

17. [17]

    ENERGY STAR (U.S. EPA / DOE). Heat & Cool Efficiently

    "If your HVAC equipment is more than 10 years old or not keeping your house comfortable, have it evaluated by a professional HVAC contractor"; check air leaks and ducts before replacing; improper installation can reduce efficiency by up to 30 percent.

    Read 2026-10-27 · Primary source

18. [18]

    U.S. Department of Energy. Energy Saver Guide: Tips on Saving Money and Energy in Your Home (2022)

    DOE: consider replacing your existing system if your heat pump or air conditioner is more than 10 years old.

    Read 2026-10-27 · Primary source

19. [19]

    U.S. Department of Energy, Federal Energy Management Program. Purchasing Energy-Efficient Residential Central Air Conditioners (updated December 2024)

    For its cost calculations, FEMP assumes an average residential central air conditioner life of 18 years (hot-humid Southeast), 25 years (hot-dry Southwest) and 24 years (northern states).

    Read 2026-10-27 · Primary source

20. [20]

    U.S. Environmental Protection Agency. Purchasing and Repairing Home Air-Conditioners or Heat Pumps (last updated August 5, 2026)

    R-22 (HCFC-22) has been the most common refrigerant in residential systems for decades; after 2020 only recycled, reclaimed or previously produced R-22 can service existing equipment; units manufactured before 2010 can still be serviced with R-22, and EPA does not require you to replace or convert them.

    Read 2026-10-27 · Primary source

21. [21]

    U.S. Environmental Protection Agency. Residential Air Conditioning and the Phaseout of HCFC-22: What You Need to Know (2020)

    U.S. production and import of R-22 ended January 1, 2020, and you may keep using it in an existing system; most air conditioners have a nameplate that identifies the refrigerant; "R-22a" is a flammable hydrocarbon blend and not an acceptable substitute.

    Read 2026-10-27 · Primary source