Mitsubishi MLZ-KX12NL One-Way Cassette 12,000 BTU

The maker's photo for this series, not this exact size; the outdoor unit grows with capacity

Mitsubishi Electric · Ceiling Cassette

Mitsubishi MLZ-KX12NL One-Way Cassette 12,000 BTU

MLZ-KX12NL / SUZ-AA12NL

~$3,484approximate retailer price at last check, equipment only

BTU/h: 12k
Volts: 208/230
Zones: 1
SEER2: 20.7
HSPF2: 10
Heats to: -4°F
Refrig.: R-454B
Covers: 500 ft²
Wi-Fi: Built in

Best forRooms where a wall head will not fit and the ceiling cavity is shallow or joisted.

Overview

The MLZ-KX12NL is Mitsubishi's one-way cassette, a slim ceiling unit that blows in a single direction, which suits a hallway, narrow bedroom or room with a low or joisted ceiling where a wall head will not fit. This pairing uses the standard SUZ-AA12NL outdoor unit rather than the Hyper-Heat HZ version, so it is rated 20.7 SEER2 and 10 HSPF2 with 11,300 BTU of cooling and 14,600 BTU of heating, and Mitsubishi's submittal rates heating operation down to -4°F. Wi-Fi runs through the Comfort app. It is the R-454B successor to the KP-series one-way cassette. Against Fujitsu's compact four-way cassette it costs more and moves air one way; the trade is a unit that sits flush in a 16 inch joist bay.

One-way flush cassette
Fits a 16 inch joist bay

Cold-weather output

At 5°F it still makes 53% of its rated heat, according to the certified NEEP listing for this pairing. Mitsubishi Electric rates it to keep running down to -4°F.

COP at 5°F: 2.17
Refrigerant: R-454B
AHRI cert.: 215734897
ENERGY STAR cold climate: No

Pairing: SUZ-AA12NL with MLZ-KX12NL. Checked October 8, 2026 on NEEP's ccASHP list; a different head or condenser posts different numbers.

Strengths and catches

Strengths

+One-way airflow suits narrow rooms and hallways better than a four-way cassette
+20.7 SEER2 and 10 HSPF2 for a cassette
+10-year parts and compressor with contractor install and registration

Catches

−About $3,500 for the system before labor, well above the Fujitsu compact cassette
−Grille is a separate part number; confirm it is in the quote
−Needs a contractor to keep the long warranty
−Standard condenser heats less in deep cold than the HZ pairing, which costs more

Questions buyers ask

Why a one-way cassette instead of a wall unit?+

A one-way cassette sits flush in the ceiling and blows across the room, so it suits a narrow room or one with no wall space for a head. It needs a framed opening between joists and a condensate path, and the MLP-449WU grille is part of the system.

Can it be primary heat in winter?+

Marginally. NEEP lists 14,600 BTU at 47°F but 7,700 BTU at 5°F, about 53%, with COP 2.17. The maker's floor is -4°F and it is not the Hyper-Heat series. For a cold climate the Hyper-Heat floor mount below is the stronger Mitsubishi.

What does a self-install cost me?+

It forfeits the 10-year parts and compressor term, which needs a licensed contractor and online registration. Standard is 5-year parts and 7-year compressor.