What is the SEER2 rating of the Trane 4TXM2318A12NU?

The Trane 4TXM2318A12NU is rated at up to 20.0 SEER2 and 12.0 EER2 for cooling and up to 10.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.

Is the Trane 4TXM2318A12NU good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 21,800 BTU/h at 5°F with a COP of 1.81, so it is still 1.8 times as efficient as electric resistance heat at that temperature.

How much does the Trane 4TXM2318A12NU cost to run per year?

At its rated efficiency it costs about $425-$1,289 a year in electricity in large U.S. cities, depending on climate and local rates - for example $545 in Phoenix and $1,093 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.

What refrigerant does the Trane 4TXM2318A12NU use?

It uses R-410A. R-410A is being phased down under the EPA AIM Act, and new systems are moving to R-454B and R-32.

18,000 BTU mini-split heat pump · 23 MZ Series

Trane 4TXM2318A12NU

Below average cooling efficiency and average heating efficiency for a 18,000 BTU mini-split heat pump, and certified for cold climates.

Ranks #399 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $524 a year to run in a mixed climate like Atlanta.

SEER2: 20.0 Cooling efficiency over a season
Below average · beats 18%
HSPF2: 10.0 Heating efficiency over a season
Average · beats 43%
EER2: 12.0 Cooling efficiency on a 95°F day
Below average · beats 25%
Heat at 5°F: 21,800 BTU/h104% of its 47°F output
Below average · beats 16%

A good fit if…

Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 21,800 BTU/h at 5°F.
You want steady temperatures and quiet running - the compressor varies its speed.

Think twice if…

Cooling cost matters most - its SEER2 is below average for mini-splits.
You want the newest refrigerant - it uses R-410A, which is being phased down.

Calculate my running cost

Details

Specifications18,000 BTU, R-410A

General
Brand	Trane
Also sold as	American Standard
Outdoor unit model	4TXM2318A12NU
Series	23 MZ Series
Type	Mini-split heat pump
Nominal size	18,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-410A
Connected (smart) capable	No
On the market since	January 1, 2023
Last certified	June 13, 2026
Cooling
SEER2Seasonal efficiency, higher is better	20.0 (range 20.0)
EER2Efficiency at 95°F outdoors	12.0
Cooling capacity	18,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	10.0
Capacity at 47°F	21,000 BTU/h
Capacity at 17°F	17,000 BTU/h
Capacity at 5°F	21,800 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.81
ENERGY STAR cold climate	Yes

Heating output as it gets colder104% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its best matchup at the standard test temperatures, in BTU/h:

Certified matchups2 indoor units

The same outdoor unit scores differently with each indoor unit. Ask your installer for the AHRI reference number of the exact system you are quoted.

Indoor unit	SEER2	EER2	HSPF2	Heat @5°F	AHRI ref.
- TRANE · cold climate	20.0	12.0	10.0	21,800	204340534
- AMERICAN STANDARD · cold climate	20.0	12.0	10.0	21,800	204340535

Yearly running cost in 10 large cities$425-$1,289

Phoenix, AZ$545/yr
Miami, FL$425/yr
Houston, TX$490/yr
Atlanta, GA$524/yr
Los Angeles, CA$517/yr
New York, NY$1,289/yr
Chicago, IL$1,053/yr
Denver, CO$881/yr
Seattle, WA$546/yr
Minneapolis, MN$1,093/yr

At each state's average electricity price and the city's typical heating and cooling hours.

Questions4

What is the SEER2 rating of the Trane 4TXM2318A12NU?: The Trane 4TXM2318A12NU is rated at up to 20.0 SEER2 and 12.0 EER2 for cooling and up to 10.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
Is the Trane 4TXM2318A12NU good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 21,800 BTU/h at 5°F with a COP of 1.81, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
How much does the Trane 4TXM2318A12NU cost to run per year?: At its rated efficiency it costs about $425-$1,289 a year in electricity in large U.S. cities, depending on climate and local rates - for example $545 in Phoenix and $1,093 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
What refrigerant does the Trane 4TXM2318A12NU use?: It uses R-410A. R-410A is being phased down under the EPA AIM Act, and new systems are moving to R-454B and R-32.

Running cost and savings

Pre-filled with this model. Pick your city and what you heat with today; everything else is optional.

Heat pump $552/yrYou save $425/yrSee details ↓

1. Where you live

StateCityElectricity ¢ per kWh

Adjust heating and cooling hours

Filled in from your city's climate. Change them if you run the system much more or less than usual.

Cooling hours full-load hours per yearHeating hours full-load hours per year

2. The heat pump Trane 4TXM2318A12NU

Find a model (fills in the ratings below)

SEER2 cooling efficiencyHSPF2 heating efficiencyCooling capacity BTU/hHeating capacity BTU/h

3. What it replaces

Current heatingFurnace efficiency (AFUE %)Gas price, $/thermCurrent coolingOld AC rating SEER2 (10 ≈ 15+ years old)

4. Price replace the example with your quote

Installed price, $Rebates and incentives, $ utility, state

Heat pump, per year: $552
Current system, per year: $977
You save per year: $425
Payback: 16.5 years
Net after 10 years: -$2,748

Cooling $317Heating $235Electricity used: 3,450 kWhSaved vs. a minimum-efficiency heat pump: $205

Estimates use the unit's rated SEER2 and HSPF2, full-load hours derived from NOAA 1991-2020 degree days, average residential electricity prices from the U.S. EIA (12 months to July 2026) and fuel prices from EIA (2025 for natural gas, week of 2026-10-05 for propane and heating oil). Very cold days that need backup heat are not modelled. Federal minimum for comparison: 14.3 SEER2 / 7.5 HSPF2.

Similar 18,000 BTU models

MOOVAIR DM18HOS25230E3A · cold climate20.0 SEER2 · 10.0 HSPF2
Mitsubishi Electric MXZ-2C20NA420.0 SEER2 · 9.9 HSPF2
Mitsubishi Electric MXZ-2D20NL20.0 SEER2 · 10.0 HSPF2
Hisense AO-18U3R25E20.0 SEER2 · 9.8 HSPF2
Fujitsu AOU18RLXFWH · cold climate20.0 SEER2 · 10.0 HSPF2
Hisense AO-18U3R25SS20.0 SEER2 · 9.8 HSPF2
Friedrich FPHFR18A3D · cold climate20.0 SEER2 · 10.0 HSPF2
LG KUMXA181A · cold climate20.0 SEER2 · 9.8 HSPF2

See all 465 18,000 BTU mini-splits, ranked

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of June 13, 2026. How we use the data.