How to find a furnace model number, and what it tells you

Where the label is on a furnace

Carrier and Goodman call it the rating plate. It is a sticker or plate the maker attaches to the cabinet. Each brand puts it in a slightly different place.

Carrier says the serial number is on the rating plate sticker, and for furnaces it is inside the front door panel. Goodman says the model and serial number are on the rating plate on the inner wall of your furnace or air handler.

Lennox says its label is behind the top-front service panel. It sits on the left side of the interior cabinet or the top of the blower deck. Lennox adds that the furnace's orientation and airflow direction may change where the information is.

Trane says to look for a manufacturer's sticker or plate on the side of your furnace. A federal recall notice for Armstrong Air and Air Ease furnaces puts it another way. The brand name is printed on the outside, and the model number is on the label found by opening the furnace door.

If you are not sure where your indoor unit is, see where air handlers are usually installed.

Start with your paperwork, not the cabinet

You may not need to open anything. Goodman says many of its dealers attach the traveler label, the shipping-box sticker, to the paperwork a homeowner gets after installation. It says this makes it unnecessary to physically view the serial number on the unit.

Goodman also says a dealer should be involved in accessing the serial number. If the only label you can find is inside the cabinet, ask the contractor who services your system to read it at the next visit. Do not touch wiring or gas parts.

Carrier says that for help locating the serial and model numbers on your unit, you can contact a local dealer. You can read and photograph labels on the outside of the cabinet, such as the one Trane describes on the side.

When you find the plate, take a clear photo of it. Write both numbers down with your home records.

Model number versus serial number

Goodman says its serial number is a ten digit code that helps identify the time the unit was produced, as well as the model number and many of the sub-components used on that unit.

For air conditioners, a Department of Energy guide says to locate the model number, not the serial number, when you want the unit's capacity.

Carrier's legacy gas furnace program asks owners to check a table of model and serial numbers to see if they qualify. We found no source that decodes every brand's codes.

What the model number can tell you about size

Trane says BTU stands for British thermal unit, and one BTU equals the heat required to raise or lower the temperature of one pound of water by one degree Fahrenheit.

Trane says that in its furnace model numbers, the BTU is the middle number, such as 040, 060, 080, 100, or 120. On its list, 040 means a 40,000 BTU furnace and 120 means a 120,000 BTU furnace.

Cooling equipment uses a different unit, the ton. The Department of Energy guide says one ton equals 12,000 Btu an hour of cooling capacity, and that capacity is often indicated in the model number. Its example is a model SSX160241, a 2-ton, or 24,000 Btu an hour, air conditioner.

The same guide says a heat pump can operate the refrigeration cycle in reverse to provide heating. See how to tell if you have a heat pump.

For how a furnace should be sized, see what size furnace you need.

The yellow EnergyGuide label

Trane says to look for the yellow Energy Guide sticker on your furnace. A federal rule in the Code of Federal Regulations (CFR), 16 CFR 305.20, sets what goes on it. Paragraph (f) of that section sets the content of labels for non-weatherized furnaces, weatherized furnaces, mobile home furnaces, electric furnaces, and boilers.

The rule says the label shows the model's basic model number. The label may list several model numbers on one label when those models share the same efficiency ratings and capacities and the information is clear and prominent. It also shows the AFUE rating, explained below. Showing the model's capacity is optional, at the discretion of the manufacturer or private labeler. The label also shows a range of comparability, the lowest and highest AFUE ratings for all furnaces of that type. The label itself states that federal law prohibits removal of this label before consumer purchase.

Trane says AFUE stands for Annual Fuel Utilization Efficiency. It measures the share of fuel a gas furnace burns to heat your home. The rest is vented out of your home as flue gas, Trane says. Trane says you can find the AFUE rating on the Energy Guide sticker. If the sticker is gone, it says to check your owner's manual.

For what those ratings mean when comparing furnaces, see furnace types and efficiency.

Recalls, matched systems and Florida homes

Recalls can name furnaces by model number. A 2023 recall notice from the Consumer Product Safety Commission (CPSC) named the recalled furnaces by model number, such as A96UH1E045B12S.

A Department of Energy guide says central air conditioners are typically installed with central furnaces and use the same blower and ducts. It says the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), an industry association, assigns a certification number and efficiency ratings to specific combinations of equipment. It adds that proper matching according to AHRI is important for equipment warranty.

The Energy Information Administration (EIA) reported that Florida had the largest share of all-electric homes of any state in 2020. The Department of Energy guide says that in warm-humid climates with moderate space heating needs, space heating is typically provided by an electric coil that heats the airstream.

In those homes, look for the rating plate on the air handler, where Goodman says its plate can be. See gas furnace versus electric heat strips for how the two differ.