What is the SEER2 rating of the Mainline ML18HP230LMNT-O?

The Mainline ML18HP230LMNT-O is rated at up to 18.8 SEER2 and 11.0 EER2 for cooling and up to 9.4 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 6 certified matchups SEER2 ranges from 16.8-18.8.

Is the Mainline ML18HP230LMNT-O good for cold climates?

It is not cold-climate certified: none of its matchups meet the ENERGY STAR cold-climate criteria (a COP of at least 1.75 at 5°F among other limits). In places with frequent sub-zero nights, pick a cold-climate 1.5-ton model.

How much does the Mainline ML18HP230LMNT-O cost to run per year?

At its rated efficiency it costs about $450-$1,208 a year in electricity in large U.S. cities, depending on climate and local rates - for example $555 in Phoenix and $1,010 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 ML18HP230LMNT-O?

ENERGY STAR lists 6 certified combinations for this outdoor unit. The highest-rated ones use ML18HP230LMNTAHU-I, ML24HP230LMNTAHU-I, ML18HP230WMAHU-I.

1.5-ton central heat pump · ML Series

Mainline ML18HP230LMNT-O

Very good cooling efficiency and average heating efficiency for a 1.5-ton central heat pump, but not rated for cold climates.

Ranks #43 of 170 1.5 ton central heat pumps for cooling efficiency, and costs about $505 a year to run in a mixed climate like Atlanta.

SEER2: 18.8 Cooling efficiency over a season
Very good · beats 81%
HSPF2: 9.4 Heating efficiency over a season
Average · beats 64%
EER2: 11.0 Cooling efficiency on a 95°F day
Below average · beats 23%
Heat at 5°F: 11,400 BTU/h62% of its 47°F output
Average · beats 58%

A good fit if…

You want low cooling bills - its SEER2 beats 81% of central heat pumps.
You want steady temperatures and quiet running - the compressor varies its speed.

Think twice if…

You often see nights below 0°F - it is not cold-climate certified.

Calculate my running cost

Details

Specifications1.5 ton, R-454B

General
Brand	Mainline
Outdoor unit model	ML18HP230LMNT-O
Series	ML Series
Type	Central heat pump
Nominal size	1.5 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	18.8 (range 16.8-18.8)
EER2Efficiency at 95°F outdoors	11.0-11.5
Cooling capacity	18,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	8.8-9.4
Capacity at 47°F	18,000 BTU/h
Capacity at 17°F	11,800-12,600 BTU/h
Capacity at 5°F	11,200-11,400 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80-2.10
ENERGY STAR cold climate	No

Heating output as it gets colder62% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML18HP230LMNTAHU-I at the standard test temperatures, in BTU/h:

Certified matchups6 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.
ML18HP230LMNTAHU-I	18.8	11.0	9.1	11,200	217607168
ML24HP230LMNTAHU-I	18.8	11.0	9.1	11,200	217607219
ML18HP230LMNTAHU-I	18.8	11.0	9.1	11,200	215864304
ML18HP230WMAHU-I	18.5	11.5	9.4	11,400	217607192
ML18HP230PCAHU-I	16.8	11.5	8.8	11,400	217607224
ML18HP230PCAHU-I	16.8	11.5	8.8	11,400	216623444

Yearly running cost in 10 large cities$450-$1,208

Phoenix, AZ$555/yr
Miami, FL$450/yr
Houston, TX$498/yr
Atlanta, GA$505/yr
Los Angeles, CA$492/yr
New York, NY$1,208/yr
Chicago, IL$981/yr
Denver, CO$816/yr
Seattle, WA$502/yr
Minneapolis, MN$1,010/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 ML18HP230LMNT-O?: The Mainline ML18HP230LMNT-O is rated at up to 18.8 SEER2 and 11.0 EER2 for cooling and up to 9.4 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 6 certified matchups SEER2 ranges from 16.8-18.8.
Is the Mainline ML18HP230LMNT-O good for cold climates?: It is not cold-climate certified: none of its matchups meet the ENERGY STAR cold-climate criteria (a COP of at least 1.75 at 5°F among other limits). In places with frequent sub-zero nights, pick a cold-climate 1.5-ton model.
How much does the Mainline ML18HP230LMNT-O cost to run per year?: At its rated efficiency it costs about $450-$1,208 a year in electricity in large U.S. cities, depending on climate and local rates - for example $555 in Phoenix and $1,010 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 ML18HP230LMNT-O?: ENERGY STAR lists 6 certified combinations for this outdoor unit. The highest-rated ones use ML18HP230LMNTAHU-I, ML24HP230LMNTAHU-I, ML18HP230WMAHU-I.
What refrigerant does the Mainline ML18HP230LMNT-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 $551/yrYou save $377/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 ML18HP230LMNT-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: $551
Current system, per year: $928
You save per year: $377
Payback: 18.6 years
Net after 10 years: -$3,234

Cooling $337Heating $214Electricity used: 3,447 kWhSaved vs. a minimum-efficiency heat pump: $160

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 1.5 ton models

Innovair SOV18H2BA18.8 SEER2 · 9.4 HSPF2
MDV MOX330-18HFN10-M318.8 SEER2 · 9.4 HSPF2
DuraSTAR DRU1U18S2A18.8 SEER2 · 9.4 HSPF2
Midea MO1BE-H18B-2A18.8 SEER2 · 9.4 HSPF2
Carrier 37MURAQ18AA318.8 SEER2 · 9.4 HSPF2
MOOVAIR MSHEA18R2AN118.8 SEER2 · 9.4 HSPF2
Arcoaire D5CURAH18AAK18.8 SEER2 · 9.4 HSPF2
1HVAC ACIQ-18-EHPD18.8 SEER2 · 9.1 HSPF2

See all 170 1.5 ton central heat pumps, ranked

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