What is the SEER2 rating of the Sea Breeze HSZ12H424ZMO?

The Sea Breeze HSZ12H424ZMO is rated at up to 24.2 SEER2 and 13.3 EER2 for cooling and up to 10.7 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 9 certified matchups SEER2 ranges from 19.5-24.2.

Is the Sea Breeze HSZ12H424ZMO good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 12,100 BTU/h at 5°F with a COP of 1.99, so it is still 2.0 times as efficient as electric resistance heat at that temperature.

How much does the Sea Breeze HSZ12H424ZMO cost to run per year?

At its rated efficiency it costs about $234-$692 a year in electricity in large U.S. cities, depending on climate and local rates - for example $298 in Phoenix and $585 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 Sea Breeze HSZ12H424ZMO?

ENERGY STAR lists 9 certified combinations for this outdoor unit. The highest-rated ones use Breeze33 C12H424ZMI, SEA BREEZE+ C12H424ZMI, SEA BREEZE+ WM12H424ZMI.

What refrigerant does the Sea Breeze HSZ12H424ZMO 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.

12,000 BTU mini-split heat pump · HS series

Sea Breeze HSZ12H424ZMO

Very good cooling efficiency and average heating efficiency for a 12,000 BTU mini-split heat pump, and certified for cold climates.

Ranks #170 of 394 12,000 BTU mini-splits for cooling efficiency, and costs about $283 a year to run in a mixed climate like Atlanta.

SEER2: 24.2 Cooling efficiency over a season
Very good · beats 78%
HSPF2: 10.7 Heating efficiency over a season
Average · beats 68%
EER2: 13.3 Cooling efficiency on a 95°F day
Very good · beats 70%
Heat at 5°F: 12,100 BTU/h99% of its 47°F output
Below average · beats 38%

A good fit if…

You want low cooling bills - its SEER2 beats 78% of mini-splits.
Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 12,100 BTU/h at 5°F.
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

Specifications12,000 BTU, R-410A

General
Brand	Sea Breeze
Also sold as	Breeze33
Outdoor unit model	HSZ12H424ZMO
Series	HS series
Type	Mini-split heat pump
Nominal size	12,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-410A
Connected (smart) capable	No
On the market since	January 1, 2022
Last certified	June 25, 2026
Cooling
SEER2Seasonal efficiency, higher is better	24.2 (range 19.5-24.2)
EER2Efficiency at 95°F outdoors	11.7-13.3
Cooling capacity	12,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	10.0-10.7
Capacity at 47°F	12,000-12,500 BTU/h
Capacity at 17°F	9,500-10,600 BTU/h
Capacity at 5°F	11,000-12,100 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80-1.99
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 matchup with C12H424ZMI 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.
C12H424ZMI Breeze33 · cold climate	24.2	13.3	10.7	11,900	211277587
C12H424ZMI SEA BREEZE+ · cold climate	24.2	13.3	10.7	11,900	212595648
WM12H424ZMI SEA BREEZE+ · cold climate	23.1	13.0	10.5	11,000	208128267
SCA12H424ZMI Breeze33 · cold climate	23.0	13.0	10.0	11,000	211277585
SCA12H424ZMI SEA BREEZE+ · cold climate	23.0	13.0	10.0	11,000	212595647
CA12H424ZMI Breeze33 · cold climate	22.3	12.7	10.2	11,300	211277584
CA12H424ZMI SEA BREEZE+ · cold climate	22.3	12.7	10.2	11,300	208128268
D12H424ZMI Breeze33 · cold climate	19.5	11.7	10.0	12,100	211277586
D12H424ZMI SEA BREEZE+ · cold climate	19.5	11.7	10.0	12,100	208128269

Yearly running cost in 10 large cities$234-$692

Phoenix, AZ$298/yr
Miami, FL$234/yr
Houston, TX$267/yr
Atlanta, GA$283/yr
Los Angeles, CA$278/yr
New York, NY$692/yr
Chicago, IL$565/yr
Denver, CO$472/yr
Seattle, WA$292/yr
Minneapolis, MN$585/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 Sea Breeze HSZ12H424ZMO?: The Sea Breeze HSZ12H424ZMO is rated at up to 24.2 SEER2 and 13.3 EER2 for cooling and up to 10.7 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with; across its 9 certified matchups SEER2 ranges from 19.5-24.2.
Is the Sea Breeze HSZ12H424ZMO good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 12,100 BTU/h at 5°F with a COP of 1.99, so it is still 2.0 times as efficient as electric resistance heat at that temperature.
How much does the Sea Breeze HSZ12H424ZMO cost to run per year?: At its rated efficiency it costs about $234-$692 a year in electricity in large U.S. cities, depending on climate and local rates - for example $298 in Phoenix and $585 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 Sea Breeze HSZ12H424ZMO?: ENERGY STAR lists 9 certified combinations for this outdoor unit. The highest-rated ones use Breeze33 C12H424ZMI, SEA BREEZE+ C12H424ZMI, SEA BREEZE+ WM12H424ZMI.
What refrigerant does the Sea Breeze HSZ12H424ZMO 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 $300/yrYou save $319/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 Sea Breeze HSZ12H424ZMO

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: $300
Current system, per year: $619
You save per year: $319
Payback: 14.1 years
Net after 10 years: -$1,314

Cooling $175Heating $126Electricity used: 1,876 kWhSaved vs. a minimum-efficiency heat pump: $174

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 12,000 BTU models

PerfectAire 3PAMSHH12-SZO · cold climate24.2 SEER2 · 10.7 HSPF2
SLIMAIR SHC12AH2AG · cold climate24.0 SEER2 · 11.6 HSPF2
Mitsutomo HO-SZ12-AB-Q · cold climate24.2 SEER2 · 10.7 HSPF2
Sharp AE-X12DWU · cold climate24.0 SEER2 · 11.0 HSPF2
KARDA 3KARDA12SZO · cold climate24.2 SEER2 · 10.7 HSPF2
ComfortStar CHF3-12CD(O) · cold climate24.0 SEER2 · 10.5 HSPF2
DuraSTAR DRA1H12S1A · cold climate24.2 SEER2 · 10.7 HSPF2
Convectair 500004492 · cold climate24.0 SEER2 · 10.5 HSPF2

See all 394 12,000 BTU mini-splits, ranked

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of June 25, 2026. How we use the data.