What is the SEER2 rating of the AUX AH18MHA2DI-20US?

The AUX AH18MHA2DI-20US is rated at up to 20.0 SEER2 and 11.0 EER2 for cooling and up to 9.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.

Is the AUX AH18MHA2DI-20US good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 14,200 BTU/h at 5°F with a COP of 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.

How much does the AUX AH18MHA2DI-20US cost to run per year?

At its rated efficiency it costs about $425-$1,300 a year in electricity in large U.S. cities, depending on climate and local rates - for example $547 in Phoenix and $1,104 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.

Is the AUX AH18MHA2DI-20US the same as the SMARTFLEX EZI18CN23STG1?

Yes, as far as the certified ratings go. ENERGY STAR lists both model numbers with identical efficiency, capacity and matchups, which means the same outdoor unit sold under a different brand or with a minor variant code (voltage, colour or region). The full list is on this page.

Which indoor units work with the AUX AH18MHA2DI-20US?

ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses AWH18MHA2DI-20US.

18,000 BTU mini-split heat pump · C-Series

AUX AH18MHA2DI-20US

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

Ranks #411 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $528 a year to run in a mixed climate like Atlanta.

SEER2: 20.0 Cooling efficiency over a season
Below average · beats 18%
HSPF2: 9.0 Heating efficiency over a season
Below average · beats 10%
EER2: 11.0 Cooling efficiency on a 95°F day
Below average · beats 9%
Heat at 5°F: 14,200 BTU/h74% of its 47°F output
Below average · beats 9%

A good fit if…

Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 14,200 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 mainly need heat - its HSPF2 is below average for mini-splits.

Calculate my running cost

Details

Specifications18,000 BTU, R-32

General
Brand	AUX
Also sold as	SMARTFLEX
Outdoor unit model	AH18MHA2DI-20US
Series	C-Series
Type	Mini-split heat pump
Nominal size	18,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-32
Connected (smart) capable	No
On the market since	February 3, 2026
Last certified	April 21, 2026
Cooling
SEER2Seasonal efficiency, higher is better	20.0 (range 20.0)
EER2Efficiency at 95°F outdoors	11.0
Cooling capacity	18,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	9.0
Capacity at 47°F	19,100 BTU/h
Capacity at 17°F	14,000 BTU/h
Capacity at 5°F	14,200 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80
ENERGY STAR cold climate	Yes

Heating output as it gets colder74% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with AWH18MHA2DI-20US at the standard test temperatures, in BTU/h:

Certified matchups1 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.
AWH18MHA2DI-20US · cold climate	20.0	11.0	9.0	14,200	218080135

Same unit, other model numbers1

These model numbers have exactly the same certified ratings and matchups as the AUX AH18MHA2DI-20US: the same equipment under another brand, or a variant code for voltage, colour or market. Everything on this page applies to them.

SMARTFLEX EZI18CN23STG1

Yearly running cost in 10 large cities$425-$1,300

Phoenix, AZ$547/yr
Miami, FL$425/yr
Houston, TX$491/yr
Atlanta, GA$528/yr
Los Angeles, CA$521/yr
New York, NY$1,300/yr
Chicago, IL$1,063/yr
Denver, CO$890/yr
Seattle, WA$551/yr
Minneapolis, MN$1,104/yr

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

Questions6

What is the SEER2 rating of the AUX AH18MHA2DI-20US?: The AUX AH18MHA2DI-20US is rated at up to 20.0 SEER2 and 11.0 EER2 for cooling and up to 9.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
Is the AUX AH18MHA2DI-20US good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 14,200 BTU/h at 5°F with a COP of 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
How much does the AUX AH18MHA2DI-20US cost to run per year?: At its rated efficiency it costs about $425-$1,300 a year in electricity in large U.S. cities, depending on climate and local rates - for example $547 in Phoenix and $1,104 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
Is the AUX AH18MHA2DI-20US the same as the SMARTFLEX EZI18CN23STG1?: Yes, as far as the certified ratings go. ENERGY STAR lists both model numbers with identical efficiency, capacity and matchups, which means the same outdoor unit sold under a different brand or with a minor variant code (voltage, colour or region). The full list is on this page.
Which indoor units work with the AUX AH18MHA2DI-20US?: ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses AWH18MHA2DI-20US.
What refrigerant does the AUX AH18MHA2DI-20US use?: It uses 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 $554/yrYou save $392/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 AUX AH18MHA2DI-20US

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: $554
Current system, per year: $946
You save per year: $392
Payback: 17.9 years
Net after 10 years: -$3,084

Cooling $317Heating $238Electricity used: 3,466 kWhSaved vs. a minimum-efficiency heat pump: $174

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

Goodman GRXTH18BVJN · cold climate20.0 SEER2 · 9.3 HSPF2
Mitsubishi Electric MUZ-HX18NL · cold climate20.0 SEER2 · 9.5 HSPF2
Hisense AO-18U3R26SS20.0 SEER2 · 9.5 HSPF2
GE Appliances 1G18CB2BE · cold climate20.0 SEER2 · 9.5 HSPF2
DELLA 048-TLP-MODU-1D2 · cold climate20.0 SEER2 · 9.0 HSPF2
GE Appliances 1G18AD2BE · cold climate20.0 SEER2 · 9.5 HSPF2
Fujitsu AOUH18KNAS1 · cold climate20.0 SEER2 · 9.0 HSPF2
Trane / Mitsubishi Electric NTXMMX20A122C20.0 SEER2 · 9.7 HSPF2

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

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of April 21, 2026. How we use the data.