What is the SEER2 rating of the Mainline ML09HP230NEXH-O?

The Mainline ML09HP230NEXH-O is rated at up to 27.2 SEER2 and 15.1 EER2 for cooling and up to 13.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 12 certified matchups SEER2 ranges from 20.5-27.2.

Is the Mainline ML09HP230NEXH-O good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 11,900 BTU/h at 5°F with a COP of 1.89, so it is still 1.9 times as efficient as electric resistance heat at that temperature.

How much does the Mainline ML09HP230NEXH-O cost to run per year?

At its rated efficiency it costs about $156-$450 a year in electricity in large U.S. cities, depending on climate and local rates - for example $197 in Phoenix and $379 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.

Which indoor units work with the Mainline ML09HP230NEXH-O?

ENERGY STAR lists 12 certified combinations for this outdoor unit. The highest-rated ones use MAINLINE ML09HP230CON-I, MAINLINE ML09HP230NEX-I, MAINLINE ML09HP2301WYCAS-I.

9,000 BTU mini-split heat pump · ML Series

Mainline ML09HP230NEXH-O

Excellent cooling and heating efficiency for a 9,000 BTU mini-split heat pump, and certified for cold climates.

Ranks #82 of 395 9,000 BTU mini-splits for cooling efficiency, and costs about $185 a year to run in a mixed climate like Atlanta.

SEER2: 27.2 Cooling efficiency over a season
Excellent · beats 95%
HSPF2: 13.8 Heating efficiency over a season
Excellent · beats 97%
EER2: 15.1 Cooling efficiency on a 95°F day
Excellent · beats 92%
Heat at 5°F: 11,900 BTU/h126% of its 47°F output
Below average · beats 22%

A good fit if…

You want low cooling bills - its SEER2 beats 95% of mini-splits.
Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 11,900 BTU/h at 5°F.
It will heat most of the year - its HSPF2 beats 97% of mini-splits.
You want steady temperatures and quiet running - the compressor varies its speed.

Think twice if…

Nothing stands out - its ratings have no weak spot for its class.

Calculate my running cost

Details

Specifications9,000 BTU, R-454B

General
Brand	Mainline
Outdoor unit model	ML09HP230NEXH-O
Series	ML Series
Type	Mini-split heat pump
Nominal size	9,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-454B
Connected (smart) capable	No
On the market since	May 20, 2024
Last certified	August 11, 2026
Cooling
SEER2Seasonal efficiency, higher is better	27.2 (range 20.5-27.2)
EER2Efficiency at 95°F outdoors	13.4-15.1
Cooling capacity	9,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	10.9-13.8
Capacity at 47°F	9,000-12,000 BTU/h
Capacity at 17°F	9,000-12,000 BTU/h
Capacity at 5°F	10,600-11,900 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80-1.89
ENERGY STAR cold climate	Yes

Heating output as it gets colder126% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML09HP230CON-I at the standard test temperatures, in BTU/h:

Certified matchups12 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.
ML09HP230CON-I MAINLINE · cold climate	27.2	15.1	10.9	11,300	217607294
ML09HP230CON-I MAINLINE · cold climate	27.2	15.1	10.9	11,300	215864381
ML09HP230NEX-I MAINLINE · cold climate	26.0	15.0	12.5	11,500	217607252
ML09HP230NEX-I MAINLINE · cold climate	26.0	15.0	12.5	11,500	215864339
ML09HP2301WYCAS-I MAINLINE · cold climate	24.0	14.6	12.1	10,600	217607300
ML09HP2301WYCAS-I MAINLINE · cold climate	24.0	14.6	12.1	10,600	215864387
ML09HP230STDCAS-I MAINLINE · cold climate	22.6	14.0	12.1	11,000	217607282
ML09HP230STDCAS-I MAINLINE · cold climate	22.6	14.0	12.1	11,000	215864369
ML09HP230LSDUC-I MAINLINE · cold climate	21.4	13.4	12.5	11,200	217607287
ML09HP230LSDUC-I MAINLINE · cold climate	21.4	13.4	12.5	11,200	215864374
ML09HP230HSDUC-I MAINLINE · cold climate	20.5	14.0	13.8	11,900	217607290
ML09HP230HSDUC-I MAINLINE · cold climate	20.5	14.0	13.8	11,900	215864377

Yearly running cost in 10 large cities$156-$450

Phoenix, AZ$197/yr
Miami, FL$156/yr
Houston, TX$177/yr
Atlanta, GA$185/yr
Los Angeles, CA$181/yr
New York, NY$450/yr
Chicago, IL$367/yr
Denver, CO$306/yr
Seattle, WA$189/yr
Minneapolis, MN$379/yr

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

Questions5

What is the SEER2 rating of the Mainline ML09HP230NEXH-O?: The Mainline ML09HP230NEXH-O is rated at up to 27.2 SEER2 and 15.1 EER2 for cooling and up to 13.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 12 certified matchups SEER2 ranges from 20.5-27.2.
Is the Mainline ML09HP230NEXH-O good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 11,900 BTU/h at 5°F with a COP of 1.89, so it is still 1.9 times as efficient as electric resistance heat at that temperature.
How much does the Mainline ML09HP230NEXH-O cost to run per year?: At its rated efficiency it costs about $156-$450 a year in electricity in large U.S. cities, depending on climate and local rates - for example $197 in Phoenix and $379 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
Which indoor units work with the Mainline ML09HP230NEXH-O?: ENERGY STAR lists 12 certified combinations for this outdoor unit. The highest-rated ones use MAINLINE ML09HP230CON-I, MAINLINE ML09HP230NEX-I, MAINLINE ML09HP2301WYCAS-I.
What refrigerant does the Mainline ML09HP230NEXH-O use?: It uses R-454B.

Running cost and savings

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

Heat pump $198/yrYou save $283/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 Mainline ML09HP230NEXH-O

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: $198
Current system, per year: $480
You save per year: $283
Payback: 12.4 years
Net after 10 years: -$672

Cooling $116Heating $81Electricity used: 1,235 kWhSaved vs. a minimum-efficiency heat pump: $173

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 9,000 BTU models

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Smart Comfort DLCPRBH09AAK · cold climate27.0 SEER2 · 15.0 HSPF2
AI AIR CONDITIONING AO25-09N2-M1H · cold climate27.2 SEER2 · 13.8 HSPF2
LG KUSAL091A · cold climate27.0 SEER2 · 13.5 HSPF2
Panasonic CU-XE9WKUA · cold climate27.3 SEER2 · 12.0 HSPF2
GE Appliances 1G09ED2BE · cold climate27.0 SEER2 · 12.0 HSPF2
NOVAIR LEA09SZ36-O · cold climate27.4 SEER2 · 12.5 HSPF2
Haier 1Q09RT2BE · cold climate27.0 SEER2 · 12.0 HSPF2

See all 395 9,000 BTU mini-splits, ranked

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of August 11, 2026. How we use the data.