What is the SEER2 rating of the MRCOOL O-HH-18-HP-C-230C-O?

The MRCOOL O-HH-18-HP-C-230C-O is rated at up to 21.4 SEER2 and 12.5 EER2 for cooling and up to 12.3 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 18.0-21.4.

Is the MRCOOL O-HH-18-HP-C-230C-O good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 18,000 BTU/h at 5°F with a COP of 2.00, so it is still 2.0 times as efficient as electric resistance heat at that temperature.

How much does the MRCOOL O-HH-18-HP-C-230C-O cost to run per year?

At its rated efficiency it costs about $373-$980 a year in electricity in large U.S. cities, depending on climate and local rates - for example $457 in Phoenix and $817 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 MRCOOL O-HH-18-HP-C-230C-O?

ENERGY STAR lists 3 certified combinations for this outdoor unit. The highest-rated ones use O-18-HP-WMAH-230C-O, CASSETTE18HP-230C-O, DUCT-18HP-230B-O.

18,000 BTU mini-split heat pump · O-HH Series

MRCOOL O-HH-18-HP-C-230C-O

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

Ranks #301 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $412 a year to run in a mixed climate like Atlanta.

SEER2: 21.4 Cooling efficiency over a season
Below average · beats 36%
HSPF2: 12.3 Heating efficiency over a season
Excellent · beats 92%
EER2: 12.5 Cooling efficiency on a 95°F day
Average · beats 44%
Heat at 5°F: 18,000 BTU/h100% of its 47°F output
Average · beats 48%

A good fit if…

Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 18,000 BTU/h at 5°F.
It will heat most of the year - its HSPF2 beats 92% of mini-splits.
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.

Calculate my running cost

Details

Specifications18,000 BTU, R-454B

General
Brand	MRCOOL
Outdoor unit model	O-HH-18-HP-C-230C-O
Series	O-HH Series
Type	Mini-split heat pump
Nominal size	18,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-454B
Connected (smart) capable	No
On the market since	October 25, 2024
Last certified	May 6, 2026
Cooling
SEER2Seasonal efficiency, higher is better	21.4 (range 18.0-21.4)
EER2Efficiency at 95°F outdoors	12.0-12.5
Cooling capacity	16,000-18,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	10.5-12.3
Capacity at 47°F	18,000-19,000 BTU/h
Capacity at 17°F	14,900-18,000 BTU/h
Capacity at 5°F	17,000-18,000 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.90-2.00
ENERGY STAR cold climate	Yes

Heating output as it gets colder100% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with O-18-HP-WMAH-230C-O at the standard test temperatures, in BTU/h:

Certified matchups3 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.
O-18-HP-WMAH-230C-O · cold climate	21.4	12.5	11.0	18,000	216032563
CASSETTE18HP-230C-O · cold climate	20.0	12.5	12.3	17,000	216032564
DUCT-18HP-230B-O · cold climate	18.0	12.0	10.5	18,000	216032565

Yearly running cost in 10 large cities$373-$980

Phoenix, AZ$457/yr
Miami, FL$373/yr
Houston, TX$410/yr
Atlanta, GA$412/yr
Los Angeles, CA$400/yr
New York, NY$980/yr
Chicago, IL$795/yr
Denver, CO$660/yr
Seattle, WA$405/yr
Minneapolis, MN$817/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 MRCOOL O-HH-18-HP-C-230C-O?: The MRCOOL O-HH-18-HP-C-230C-O is rated at up to 21.4 SEER2 and 12.5 EER2 for cooling and up to 12.3 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 18.0-21.4.
Is the MRCOOL O-HH-18-HP-C-230C-O good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 18,000 BTU/h at 5°F with a COP of 2.00, so it is still 2.0 times as efficient as electric resistance heat at that temperature.
How much does the MRCOOL O-HH-18-HP-C-230C-O cost to run per year?: At its rated efficiency it costs about $373-$980 a year in electricity in large U.S. cities, depending on climate and local rates - for example $457 in Phoenix and $817 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 MRCOOL O-HH-18-HP-C-230C-O?: ENERGY STAR lists 3 certified combinations for this outdoor unit. The highest-rated ones use O-18-HP-WMAH-230C-O, CASSETTE18HP-230C-O, DUCT-18HP-230B-O.
What refrigerant does the MRCOOL O-HH-18-HP-C-230C-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 $453/yrYou save $457/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 MRCOOL O-HH-18-HP-C-230C-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: $453
Current system, per year: $909
You save per year: $457
Payback: 14.2 years
Net after 10 years: -$1,933

Cooling $280Heating $173Electricity used: 2,829 kWhSaved vs. a minimum-efficiency heat pump: $250

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

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Midea MO1HS-H18B-2A · cold climate21.4 SEER2 · 12.3 HSPF2
Senville SENA-18HF-OG · cold climate21.4 SEER2 · 12.3 HSPF2
KERR A-KHP18SA-1 · cold climate21.4 SEER2 · 12.3 HSPF2
Stelpro SEPB-H18A-O · cold climate21.4 SEER2 · 12.3 HSPF2
ECO-AIR EDSO-18H · cold climate21.4 SEER2 · 12.3 HSPF2
Cooper&Hunter CH-RHP15-230VO · cold climate21.4 SEER2 · 11.0 HSPF2

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

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of May 6, 2026. How we use the data.