What is the SEER2 rating of the Lennox MLB009S4S-1P?

The Lennox MLB009S4S-1P is rated at up to 28.1 SEER2 and 16.2 EER2 for cooling and up to 12.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 9 certified matchups SEER2 ranges from 20.2-28.1.

Is the Lennox MLB009S4S-1P good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 10,800 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 Lennox MLB009S4S-1P cost to run per year?

At its rated efficiency it costs about $152-$503 a year in electricity in large U.S. cities, depending on climate and local rates - for example $201 in Phoenix and $430 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 Lennox MLB009S4S-1P?

ENERGY STAR lists 9 certified combinations for this outdoor unit. The highest-rated ones use LENNOX MWMC009S4-1P, LENNOX MWMC009S4-*P, LENNOX MWMC009S4.

What refrigerant does the Lennox MLB009S4S-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.

9,000 BTU mini-split heat pump · M series

Lennox MLB009S4S-1P

Excellent cooling efficiency and very good heating efficiency for a 9,000 BTU mini-split heat pump, and certified for cold climates.

Ranks #49 of 395 9,000 BTU mini-splits for cooling efficiency, and costs about $201 a year to run in a mixed climate like Atlanta.

SEER2: 28.1 Cooling efficiency over a season
Excellent · beats 97%
HSPF2: 12.0 Heating efficiency over a season
Very good · beats 89%
EER2: 16.2 Cooling efficiency on a 95°F day
Excellent · beats 97%
Heat at 5°F: 10,800 BTU/h88% of its 47°F output
Average · beats 48%

A good fit if…

You want low cooling bills - its SEER2 beats 97% of mini-splits.
Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 10,800 BTU/h at 5°F.
It will heat most of the year - its HSPF2 beats 89% of mini-splits.
You want steady temperatures and quiet running - the compressor varies its speed.

Think twice if…

You want the newest refrigerant - it uses R-410A, which is being phased down.

Calculate my running cost

Details

Specifications9,000 BTU, R-410A

General
Brand	Lennox
Outdoor unit model	MLB009S4S-1P
Series	M series
Type	Mini-split heat pump
Nominal size	9,000 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	28.1 (range 20.2-28.1)
EER2Efficiency at 95°F outdoors	13.0-16.2
Cooling capacity	8,800-9,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	10.2-12.0
Capacity at 47°F	9,800-12,000 BTU/h
Capacity at 17°F	9,000-10,100 BTU/h
Capacity at 5°F	10,000-10,800 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80-2.00
ENERGY STAR cold climate	Yes

Heating output as it gets colder88% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with MWMC009S4-1P at the standard test temperatures, in BTU/h:

Certified matchups9 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.
MWMC009S4-1P LENNOX · cold climate	28.1	16.2	11.5	10,600	207683520
MWMC009S4-*P LENNOX · cold climate	28.1	16.2	11.5	10,600	211034440
MWMC009S4 LENNOX · cold climate	28.1	16.2	11.5	10,600	210665627
M22A009S4-*P LENNOX · cold climate	20.5	13.0	10.2	10,000	211034455
M22A009S4-2P LENNOX · cold climate	20.5	13.0	10.2	10,000	207683531
M22A009S4 LENNOX · cold climate	20.5	13.0	10.2	10,000	210665642
MMDB009S4-2P LENNOX · cold climate	20.2	13.2	12.0	10,800	207683524
MMDB009S4-*P LENNOX · cold climate	20.2	13.2	12.0	10,800	211034444
MMDB009S4 LENNOX · cold climate	20.2	13.2	12.0	10,800	210665631

Yearly running cost in 10 large cities$152-$503

Phoenix, AZ$201/yr
Miami, FL$152/yr
Houston, TX$180/yr
Atlanta, GA$201/yr
Los Angeles, CA$200/yr
New York, NY$503/yr
Chicago, IL$412/yr
Denver, CO$346/yr
Seattle, WA$216/yr
Minneapolis, MN$430/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 MLB009S4S-1P?: The Lennox MLB009S4S-1P is rated at up to 28.1 SEER2 and 16.2 EER2 for cooling and up to 12.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 9 certified matchups SEER2 ranges from 20.2-28.1.
Is the Lennox MLB009S4S-1P good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 10,800 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 Lennox MLB009S4S-1P cost to run per year?: At its rated efficiency it costs about $152-$503 a year in electricity in large U.S. cities, depending on climate and local rates - for example $201 in Phoenix and $430 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 Lennox MLB009S4S-1P?: ENERGY STAR lists 9 certified combinations for this outdoor unit. The highest-rated ones use LENNOX MWMC009S4-1P, LENNOX MWMC009S4-*P, LENNOX MWMC009S4.
What refrigerant does the Lennox MLB009S4S-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 $206/yrYou save $274/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 MLB009S4S-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: $206
Current system, per year: $480
You save per year: $274
Payback: 12.8 years
Net after 10 years: -$756

Cooling $113Heating $93Electricity used: 1,288 kWhSaved vs. a minimum-efficiency heat pump: $165

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 9,000 BTU models

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DIRECT AIR DIRM-09HXPRO28-1Z · cold climate28.1 SEER2 · 12.0 HSPF2
TRUST AIR CONDITIONERS OAH09H/O4S4P · cold climate28.1 SEER2 · 12.0 HSPF2
Comfort-Aire A-VMH09SV-1 · cold climate28.1 SEER2 · 12.0 HSPF2
NOVAIR LEA09SZ35SK-O · cold climate28.1 SEER2 · 11.6 HSPF2
Bosch BMS500-AAS009-1CSXHC · cold climate28.1 SEER2 · 12.0 HSPF2
CanAir C28SCH09H21 · cold climate28.1 SEER2 · 11.5 HSPF2

See all 395 9,000 BTU mini-splits, ranked

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