What is the SEER2 rating of the Mainline ML24HP230LMNT-O?

The Mainline ML24HP230LMNT-O is rated at up to 18.1 SEER2 and 11.0 EER2 for cooling and up to 10.4 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 18 certified matchups SEER2 ranges from 16.0-18.1.

Is the Mainline ML24HP230LMNT-O good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 21,600 BTU/h at 5°F with a COP of 1.96, so it is still 2.0 times as efficient as electric resistance heat at that temperature.

How much does the Mainline ML24HP230LMNT-O cost to run per year?

At its rated efficiency it costs about $621-$1,547 a year in electricity in large U.S. cities, depending on climate and local rates - for example $750 in Phoenix and $1,280 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 ML24HP230LMNT-O?

ENERGY STAR lists 18 certified combinations for this outdoor unit. The highest-rated ones use ML24HP230LMNTAHU-I, ML24HP230WMAHU-I, ML24HP230CC17-I.

2-ton central heat pump · ML Series

Mainline ML24HP230LMNT-O

Very good cooling efficiency and excellent heating efficiency for a 2-ton central heat pump, and certified for cold climates.

Ranks #137 of 331 2 ton central heat pumps for cooling efficiency, and costs about $658 a year to run in a mixed climate like Atlanta.

SEER2: 18.1 Cooling efficiency over a season
Very good · beats 71%
HSPF2: 10.4 Heating efficiency over a season
Excellent · beats 94%
EER2: 11.0 Cooling efficiency on a 95°F day
Below average · beats 23%
Heat at 5°F: 21,600 BTU/h83% of its 47°F output
Below average · beats 29%

A good fit if…

You want low cooling bills - its SEER2 beats 71% of central heat pumps.
Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 21,600 BTU/h at 5°F.
It will heat most of the year - its HSPF2 beats 94% of central heat pumps.
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

Specifications2 ton, R-454B

General
Brand	Mainline
Outdoor unit model	ML24HP230LMNT-O
Series	ML Series
Type	Central heat pump
Nominal size	2 ton
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 20, 2026
Cooling
SEER2Seasonal efficiency, higher is better	18.1 (range 16.0-18.1)
EER2Efficiency at 95°F outdoors	10.0-11.0
Cooling capacity	24,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	8.5-10.4
Capacity at 47°F	24,000-26,000 BTU/h
Capacity at 17°F	18,000-20,800 BTU/h
Capacity at 5°F	19,000-21,600 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80-1.96
ENERGY STAR cold climate	Yes

Heating output as it gets colder83% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML24HP230LMNTAHU-I at the standard test temperatures, in BTU/h:

Certified matchups18 indoor units

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

Indoor unit	Furnace	SEER2	EER2	HSPF2	Heat @5°F	AHRI ref.
ML24HP230LMNTAHU-I · cold climate	-	18.1	11.0	9.7	21,600	217607169
ML24HP230LMNTAHU-I · cold climate	-	18.1	11.0	9.7	21,600	215864305
ML24HP230WMAHU-I · cold climate	-	17.4	10.8	10.4	19,600	217607193
ML24HP230WMAHU-I · cold climate	-	17.4	10.8	10.4	19,600	216623409
ML24HP230CC17-I · cold climate	S9V2B040U3VS***	17.2	10.5	8.5	20,000	217607229
ML24HP230CC17-I · cold climate	S9V2B060D3VS***	17.2	10.5	8.5	20,000	217607231
ML24HP230CC17-I · cold climate	S9V2B060U4VS***	17.2	10.5	8.5	20,000	217607230
ML24HP230CC17-I · cold climate	S9V2B040U3VS***	17.2	10.5	8.5	20,000	217550363
ML24HP230CC17-I · cold climate	S9V2B060U4VS***	17.2	10.5	8.5	20,000	217550364
ML24HP230CC17-I · cold climate	S9V2B060D3VS***	17.2	10.5	8.5	20,000	217550365
ML24HP230PCAHU-I · cold climate	-	16.0	10.0	9.0	19,000	217607200
ML24HP230CC14-I · cold climate	-	16.0	10.0	9.0	19,000	217607206
ML24HP230CC17-I · cold climate	-	16.0	10.0	9.0	19,000	217607207
ML24HP230CC17-I · cold climate	-	16.0	10.0	9.0	19,000	216623426
ML24HP230CC14-I · cold climate	-	16.0	10.0	9.0	19,000	216623425
ML24HP230PCAHU-I · cold climate	-	16.0	10.0	9.0	19,000	216623416
ML24HP230UC14-I · cold climate	-	16.0	10.0	9.0	19,000	217902705
ML24HP230UC17-I · cold climate	-	16.0	10.0	9.0	19,000	217902706

Yearly running cost in 10 large cities$621-$1,547

Phoenix, AZ$750/yr
Miami, FL$621/yr
Houston, TX$672/yr
Atlanta, GA$658/yr
Los Angeles, CA$636/yr
New York, NY$1,547/yr
Chicago, IL$1,251/yr
Denver, CO$1,036/yr
Seattle, WA$633/yr
Minneapolis, MN$1,280/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 ML24HP230LMNT-O?: The Mainline ML24HP230LMNT-O is rated at up to 18.1 SEER2 and 11.0 EER2 for cooling and up to 10.4 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 18 certified matchups SEER2 ranges from 16.0-18.1.
Is the Mainline ML24HP230LMNT-O good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 21,600 BTU/h at 5°F with a COP of 1.96, so it is still 2.0 times as efficient as electric resistance heat at that temperature.
How much does the Mainline ML24HP230LMNT-O cost to run per year?: At its rated efficiency it costs about $621-$1,547 a year in electricity in large U.S. cities, depending on climate and local rates - for example $750 in Phoenix and $1,280 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 ML24HP230LMNT-O?: ENERGY STAR lists 18 certified combinations for this outdoor unit. The highest-rated ones use ML24HP230LMNTAHU-I, ML24HP230WMAHU-I, ML24HP230CC17-I.
What refrigerant does the Mainline ML24HP230LMNT-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 $736/yrYou save $518/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 ML24HP230LMNT-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: $736
Current system, per year: $1,254
You save per year: $518
Payback: 17.4 years
Net after 10 years: -$3,821

Cooling $467Heating $269Electricity used: 4,600 kWhSaved vs. a minimum-efficiency heat pump: $228

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.

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See all 331 2 ton central heat pumps, ranked

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of August 20, 2026. How we use the data.