What is the SEER2 rating of the Lennox MLB018S4M-1P?

The Lennox MLB018S4M-1P is rated at up to 21.7 SEER2 and 12.5 EER2 for cooling and up to 9.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 19.0-21.7.

Is the Lennox MLB018S4M-1P good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 19,700 BTU/h at 5°F with a COP of 1.90, so it is still 1.9 times as efficient as electric resistance heat at that temperature.

How much does the Lennox MLB018S4M-1P cost to run per year?

At its rated efficiency it costs about $414-$1,253 a year in electricity in large U.S. cities, depending on climate and local rates - for example $530 in Phoenix and $1,062 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.

Is the Lennox MLB018S4M-1P the same as the MDV M2OI-18HFN1-M-L?

Yes, as far as the certified ratings go. ENERGY STAR lists both model numbers with identical efficiency, capacity and matchups, which means the same outdoor unit sold under a different brand or with a minor variant code (voltage, colour or region). The full list is on this page.

What refrigerant does the Lennox MLB018S4M-1P use?

It uses R-410A. R-410A is being phased down under the EPA AIM Act, and new systems are moving to R-454B and R-32.

18,000 BTU mini-split heat pump · M series

Lennox MLB018S4M-1P

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

Ranks #255 of 465 18,000 BTU mini-splits for cooling efficiency, and costs about $510 a year to run in a mixed climate like Atlanta.

SEER2: 21.7 Cooling efficiency over a season
Average · beats 42%
HSPF2: 9.8 Heating efficiency over a season
Below average · beats 33%
EER2: 12.5 Cooling efficiency on a 95°F day
Average · beats 44%
Heat at 5°F: 19,700 BTU/h99% of its 47°F output
Below average · beats 27%

A good fit if…

Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 19,700 BTU/h at 5°F.
You want steady temperatures and quiet running - the compressor varies its speed.

Think twice if…

You mainly need heat - its HSPF2 is below average for mini-splits.
You want the newest refrigerant - it uses R-410A, which is being phased down.

Calculate my running cost

Details

Specifications18,000 BTU, R-410A

General
Brand	Lennox
Also sold as	MDV
Outdoor unit model	MLB018S4M-1P
Series	M series
Type	Mini-split heat pump
Nominal size	18,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-410A
Connected (smart) capable	No
On the market since	December 18, 2019
Last certified	June 13, 2026
Cooling
SEER2Seasonal efficiency, higher is better	21.7 (range 19.0-21.7)
EER2Efficiency at 95°F outdoors	12.0-12.5
Cooling capacity	19,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	9.3-9.8
Capacity at 47°F	20,000 BTU/h
Capacity at 17°F	15,000-16,000 BTU/h
Capacity at 5°F	19,000-19,700 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.85-1.90
ENERGY STAR cold climate	Yes

Heating output as it gets colder99% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its best matchup 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.
- LENNOX · cold climate	21.7	12.5	9.8	19,700	207768727
- LENNOX · cold climate	20.4	12.3	9.6	19,300	207768729
- LENNOX · cold climate	19.0	12.0	9.3	19,000	207768728

Same unit, other model numbers1

These model numbers have exactly the same certified ratings and matchups as the Lennox MLB018S4M-1P: the same equipment under another brand, or a variant code for voltage, colour or market. Everything on this page applies to them.

MDV M2OI-18HFN1-M-L

Yearly running cost in 10 large cities$414-$1,253

Phoenix, AZ$530/yr
Miami, FL$414/yr
Houston, TX$476/yr
Atlanta, GA$510/yr
Los Angeles, CA$502/yr
New York, NY$1,253/yr
Chicago, IL$1,024/yr
Denver, CO$857/yr
Seattle, WA$531/yr
Minneapolis, MN$1,062/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 Lennox MLB018S4M-1P?: The Lennox MLB018S4M-1P is rated at up to 21.7 SEER2 and 12.5 EER2 for cooling and up to 9.8 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 3 certified matchups SEER2 ranges from 19.0-21.7.
Is the Lennox MLB018S4M-1P good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 19,700 BTU/h at 5°F with a COP of 1.90, so it is still 1.9 times as efficient as electric resistance heat at that temperature.
How much does the Lennox MLB018S4M-1P cost to run per year?: At its rated efficiency it costs about $414-$1,253 a year in electricity in large U.S. cities, depending on climate and local rates - for example $530 in Phoenix and $1,062 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
Is the Lennox MLB018S4M-1P the same as the MDV M2OI-18HFN1-M-L?: Yes, as far as the certified ratings go. ENERGY STAR lists both model numbers with identical efficiency, capacity and matchups, which means the same outdoor unit sold under a different brand or with a minor variant code (voltage, colour or region). The full list is on this page.
What refrigerant does the Lennox MLB018S4M-1P use?: It uses R-410A. R-410A is being phased down under the EPA AIM Act, and new systems are moving to R-454B and R-32.

Running cost and savings

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

Heat pump $537/yrYou save $459/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 Lennox MLB018S4M-1P

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: $537
Current system, per year: $996
You save per year: $459
Payback: 15.2 years
Net after 10 years: -$2,407

Cooling $308Heating $229Electricity used: 3,355 kWhSaved vs. a minimum-efficiency heat pump: $230

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

ZERO ZMSB-18HV-USHHCR2-O · cold climate21.7 SEER2 · 10.8 HSPF2
Arcoaire D5CSHAH18AAK · cold climate21.5 SEER2 · 12.4 HSPF2
Convectair 500004494 · cold climate21.7 SEER2 · 10.8 HSPF2
Carrier 37MAHAQ18AA3 · cold climate21.5 SEER2 · 12.4 HSPF2
ComfortStar CHF3-18CD(O) · cold climate21.7 SEER2 · 10.8 HSPF2
York YRACXJ18WHAA · cold climate21.5 SEER2 · 11.5 HSPF2
Wells WOS-18PRE/230 · cold climate21.7 SEER2 · 12.3 HSPF2
Blueridge BMY18HH22C · cold climate21.5 SEER2 · 11.3 HSPF2

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

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of June 13, 2026. How we use the data.