What is the SEER2 rating of the ZERO ZMSB-24HVT-USHHCR2?

The ZERO ZMSB-24HVT-USHHCR2 is rated at up to 22.5 SEER2 and 11.7 EER2 for cooling and up to 10.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.

Is the ZERO ZMSB-24HVT-USHHCR2 good for cold climates?

Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 22,400 BTU/h at 5°F with a COP of 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.

How much does the ZERO ZMSB-24HVT-USHHCR2 cost to run per year?

At its rated efficiency it costs about $503-$1,482 a year in electricity in large U.S. cities, depending on climate and local rates - for example $639 in Phoenix and $1,253 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.

Is the ZERO ZMSB-24HVT-USHHCR2 the same as the NOVAIR LEA24SZ-454-O?

Yes, as far as the certified ratings go. ENERGY STAR lists 5 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.

Which indoor units work with the ZERO ZMSB-24HVT-USHHCR2?

ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses ZMSB-24HVT-USHHCR2.

24,000 BTU mini-split heat pump · Z-MAX

ZERO ZMSB-24HVT-USHHCR2

Average cooling and heating efficiency for a 24,000 BTU mini-split heat pump, and certified for cold climates.

Ranks #136 of 430 24,000 BTU mini-splits for cooling efficiency, and costs about $607 a year to run in a mixed climate like Atlanta.

SEER2: 22.5 Cooling efficiency over a season
Average · beats 56%
HSPF2: 10.0 Heating efficiency over a season
Average · beats 43%
EER2: 11.7 Cooling efficiency on a 95°F day
Below average · beats 16%
Heat at 5°F: 22,400 BTU/h93% of its 47°F output
Below average · beats 9%

A good fit if…

Your winters get properly cold - it is ENERGY STAR cold-climate certified, with 22,400 BTU/h at 5°F.
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

Specifications24,000 BTU, R-454B

General
Brand	ZERO
Also sold as	NOVAIR, Pioneer, DELLA, VENTAGEN
Outdoor unit model	ZMSB-24HVT-USHHCR2
Series	Z-MAX
Type	Mini-split heat pump
Nominal size	24,000 BTU
CompressorVariable-speed units run longer at low power	Continuously variable
Refrigerant	R-454B
Connected (smart) capable	No
On the market since	November 20, 2024
Last certified	January 7, 2026
Cooling
SEER2Seasonal efficiency, higher is better	22.5 (range 22.5)
EER2Efficiency at 95°F outdoors	11.7
Cooling capacity	24,000 BTU/h
Heating
HSPF2Seasonal efficiency, higher is better	10.0
Capacity at 47°F	24,000 BTU/h
Capacity at 17°F	24,000 BTU/h
Capacity at 5°F	22,400 BTU/h
COP at 5°F2.0 = twice as efficient as a space heater	1.80
ENERGY STAR cold climate	Yes

Heating output as it gets colder93% kept at 5°F

Every heat pump delivers less heat as the outdoor temperature drops. Certified output of its matchup with ZMSB-24HVT-USHHCR2 at the standard test temperatures, in BTU/h:

Certified matchups1 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.
ZMSB-24HVT-USHHCR2 · cold climate	22.5	11.7	10.0	22,400	216723131

Same unit, other model numbers4

These model numbers have exactly the same certified ratings and matchups as the ZERO ZMSB-24HVT-USHHCR2: the same equipment under another brand, or a variant code for voltage, colour or market. Everything on this page applies to them.

NOVAIR LEA24SZ-454-O
Pioneer YN024GLSI25RPH
DELLA 048-C-TPH-24K2V-23S-OUT
VENTAGEN TSVH24HEI2N24O454

Yearly running cost in 10 large cities$503-$1,482

Phoenix, AZ$639/yr
Miami, FL$503/yr
Houston, TX$574/yr
Atlanta, GA$607/yr
Los Angeles, CA$596/yr
New York, NY$1,482/yr
Chicago, IL$1,210/yr
Denver, CO$1,011/yr
Seattle, WA$625/yr
Minneapolis, MN$1,253/yr

At each state's average electricity price and the city's typical heating and cooling hours.

Questions6

What is the SEER2 rating of the ZERO ZMSB-24HVT-USHHCR2?: The ZERO ZMSB-24HVT-USHHCR2 is rated at up to 22.5 SEER2 and 11.7 EER2 for cooling and up to 10.0 HSPF2 for heating. The exact figure depends on the indoor unit it is paired with.
Is the ZERO ZMSB-24HVT-USHHCR2 good for cold climates?: Yes. At least one certified matchup meets the ENERGY STAR cold-climate criteria, delivering up to 22,400 BTU/h at 5°F with a COP of 1.80, so it is still 1.8 times as efficient as electric resistance heat at that temperature.
How much does the ZERO ZMSB-24HVT-USHHCR2 cost to run per year?: At its rated efficiency it costs about $503-$1,482 a year in electricity in large U.S. cities, depending on climate and local rates - for example $639 in Phoenix and $1,253 in Minneapolis. The calculator on this page works it out for your city and compares it with your current system.
Is the ZERO ZMSB-24HVT-USHHCR2 the same as the NOVAIR LEA24SZ-454-O?: Yes, as far as the certified ratings go. ENERGY STAR lists 5 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.
Which indoor units work with the ZERO ZMSB-24HVT-USHHCR2?: ENERGY STAR lists 1 certified combination for this outdoor unit. The highest-rated one uses ZMSB-24HVT-USHHCR2.
What refrigerant does the ZERO ZMSB-24HVT-USHHCR2 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 $644/yrYou save $593/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 ZERO ZMSB-24HVT-USHHCR2

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: $644
Current system, per year: $1,238
You save per year: $593
Payback: 15.2 years
Net after 10 years: -$3,068

Cooling $375Heating $269Electricity used: 4,027 kWhSaved vs. a minimum-efficiency heat pump: $305

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 24,000 BTU models

TCL TSH24HEI2NAN0T24U · cold climate22.5 SEER2 · 10.0 HSPF2
LG KUMXB241A22.5 SEER2 · 9.8 HSPF2
MDV M3OX430-27HFN8-M1 · cold climate22.5 SEER2 · 10.0 HSPF2
Friedrich FPHSR24A3B · cold climate22.5 SEER2 · 9.5 HSPF2
DELLA 048-TPH-24K2V-23S-OUT · cold climate22.5 SEER2 · 10.0 HSPF2
Friedrich FPHSR24A3D · cold climate22.5 SEER2 · 9.5 HSPF2
ROVSUN RVC-24/O · cold climate22.5 SEER2 · 10.4 HSPF2
Guardian URC24CN23STG1 · cold climate22.5 SEER2 · 9.5 HSPF2

See all 430 24,000 BTU mini-splits, ranked

Source: ENERGY STAR Certified Heat Pumps (U.S. EPA), certification of January 7, 2026. How we use the data.