What is the SEER2 rating of the Mainline ML33HP230LMNTH-O?

The Mainline ML33HP230LMNTH-O is rated at up to 17.7 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; across its 4 certified matchups SEER2 ranges from 16.5-17.7.

Is the Mainline ML33HP230LMNTH-O good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 32,600 BTU/h at 5°F with a COP of 2.06, so it is still 2.1 times as efficient as electric resistance heat at that temperature.

How much does the Mainline ML33HP230LMNTH-O cost to run per year?

At its rated efficiency it costs about $953-$2,379 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,151 in Phoenix and $1,970 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 ML33HP230LMNTH-O?

ENERGY STAR lists 4 certified combinations for this outdoor unit. The highest-rated ones use ML36HP230G3AHU-I, ML36HP230LMNTAHU-I.

3-ton central heat pump · ML Series

Mainline ML33HP230LMNTH-O

Average cooling efficiency and very good heating efficiency for a 3-ton central heat pump, and certified for cold climates.

Ranks #119 of 302 3 ton central heat pumps for cooling efficiency, and costs about $1,012 a year to run in a mixed climate like Atlanta.

SEER2: 17.7 Cooling efficiency over a season
Average · beats 62%
HSPF2: 10.0 Heating efficiency over a season
Very good · beats 84%
EER2: 12.0 Cooling efficiency on a 95°F day
Average · beats 64%
Heat at 5°F: 32,600 BTU/h91% of its 47°F output
Average · beats 51%

A good fit if…

Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 32,600 BTU/h at 5°F.
It will heat most of the year - its HSPF2 beats 84% 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

Specifications3 ton, R-454B

General
Brand	Mainline
Outdoor unit model	ML33HP230LMNTH-O
Series	ML Series
Type	Central heat pump
Nominal size	3 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 19, 2026
Cooling
SEER2Seasonal efficiency, higher is better	17.7 (range 16.5-17.7)
EER2Efficiency at 95°F outdoors	10.0-12.0
Cooling capacity	36,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	8.2-10.0
Capacity at 47°F	36,000-37,000 BTU/h
Capacity at 17°F	23,200-27,600 BTU/h
Capacity at 5°F	32,000-32,600 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.85-2.06
ENERGY STAR cold climate	Yes

Heating output as it gets colder91% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ML36HP230G3AHU-I at the standard test temperatures, in BTU/h:

Certified matchups4 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.
ML36HP230G3AHU-I · cold climate	17.7	12.0	10.0	32,600	217607185
ML36HP230G3AHU-I · cold climate	17.7	12.0	10.0	32,600	216623401
ML36HP230LMNTAHU-I · cold climate	16.5	10.0	8.2	32,000	217607176
ML36HP230LMNTAHU-I · cold climate	16.5	10.0	8.2	32,000	215864313

Yearly running cost in 10 large cities$953-$2,379

Phoenix, AZ$1,151/yr
Miami, FL$953/yr
Houston, TX$1,031/yr
Atlanta, GA$1,012/yr
Los Angeles, CA$977/yr
New York, NY$2,379/yr
Chicago, IL$1,924/yr
Denver, CO$1,594/yr
Seattle, WA$974/yr
Minneapolis, MN$1,970/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 ML33HP230LMNTH-O?: The Mainline ML33HP230LMNTH-O is rated at up to 17.7 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; across its 4 certified matchups SEER2 ranges from 16.5-17.7.
Is the Mainline ML33HP230LMNTH-O good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 32,600 BTU/h at 5°F with a COP of 2.06, so it is still 2.1 times as efficient as electric resistance heat at that temperature.
How much does the Mainline ML33HP230LMNTH-O cost to run per year?: At its rated efficiency it costs about $953-$2,379 a year in electricity in large U.S. cities, depending on climate and local rates - for example $1,151 in Phoenix and $1,970 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 ML33HP230LMNTH-O?: ENERGY STAR lists 4 certified combinations for this outdoor unit. The highest-rated ones use ML36HP230G3AHU-I, ML36HP230LMNTAHU-I.
What refrigerant does the Mainline ML33HP230LMNTH-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 $1,130/yrYou save $742/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 ML33HP230LMNTH-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: $1,130
Current system, per year: $1,873
You save per year: $742
Payback: 18.2 years
Net after 10 years: -$6,077

Cooling $716Heating $414Electricity used: 7,065 kWhSaved vs. a minimum-efficiency heat pump: $308

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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Midea MO1HE-H36B-2A · cold climate17.7 SEER2 · 10.0 HSPF2
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See all 302 3 ton central heat pumps, ranked

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of August 19, 2026. How we use the data.