Cassettefrom $1,312
What is the MRCOOL DIY 5th Gen ceiling cassette, and who is it for?
Short answer: It is the OuttaSight one-way cassette, an indoor unit that sits up in the ceiling between standard 16 in joists and comes in 6K, 9K, 12K and 18K. You can buy the 18K as a single zone system for $3,418, or add cassettes to a 5th Gen multi-zone from $1,312 each (prices as of November 2026). It fits rooms with attic access above them, and you should skip it for any room with a finished floor overhead.
This is our product guide to the MRCOOL DIY 5th Gen ceiling cassette: what it is, the sizes, how you can buy each one, what it costs with the extras, and the homes it doesn't suit. If you are still choosing between a cassette and a wall unit, or you're ready to install, we cover those in separate articles linked below.
What is the OuttaSight one-way cassette?
It is MRCOOL's ceiling-mounted indoor unit for the DIY 5th Gen line. The body of the unit sits inside the ceiling cavity, and from the room you see a white panel. Air leaves from one side of that panel, which is what "one-way" means.
MRCOOL says it fits between standard 16 in ceiling joists, including I-joists, so it hangs in the bay between two joists instead of needing one cut out. The required cavity depth is in the installation manual for your size.
Inside, it is the same 5th Gen inverter heat pump as the wall units. It cools, heats and dehumidifies, runs on R-454B refrigerant, connects with pre-charged Quick Connect line sets, and works with the remote, the MRCOOL app, Alexa and Google Assistant. The 5th Gen line is rated to heat down to −13°F.
What sizes are there, and how can you buy each one?
Only the 18K comes as a single zone. The smaller sizes are sold for multi-zone systems, where one outdoor unit runs several rooms.
| Cassette size | As a single zone | On a 5th Gen multi-zone | Line set pipe size |
|---|---|---|---|
| 6K | no | yes | 1/4 x 3/8 in |
| 9K | no | yes | 1/4 x 3/8 in |
| 12K | no | yes | 1/4 x 3/8 in |
| 18K | yes, $3,418 with a 25 ft line set | yes, on outdoor units larger than 18K | 1/4 x 1/2 in |
The 18K multi-zone outdoor unit takes indoor units up to 12K, so an 18K cassette needs the 27K outdoor unit or bigger. Room size decides which cassette you need, so run each room through our sizing guide before you look at prices.
Should you buy the 18K single zone cassette or cassette rooms on a multi-zone?
Buy the 18K single zone cassette system when you have one large room to do, like a living room or a big primary bedroom. You get the cassette, its own outdoor unit and a 25 ft pre-charged line set for $3,418. That room never shares capacity with anything else.
Go multi-zone when you want cassettes in two or more rooms, or smaller cassettes than 18K. Complete cassette systems start from $4,633 for two rooms. You can also buy the OuttaSight cassette on its own, from $1,312, alongside a multi-zone outdoor unit (from $1,555) and a line set for each room.
A single small room is the awkward case. There is no 9K or 12K single zone cassette, so for one small bedroom you either put the cassette on a multi-zone you plan to grow, or you use a 9K or 12K wall single zone. Putting an 18K cassette in a 300 sq ft room is oversizing, and an oversized system tends to leave a room cool but clammy in summer.
Watch how the cassette body goes up into the ceiling and how little of it shows once the panel is on.
Next: Is a cassette worth the extra money over a wall unit in your room?
What does a cassette cost once you add the extras?
No MRCOOL system includes the disconnect, whip, pad or bracket, wire or breaker. Here is a realistic parts list for the two most common cassette purchases:
| Item | 18K single zone cassette | 2-room cassette multi-zone |
|---|---|---|
| System | $3,418 | from $4,633 |
| 60A non-fused disconnect | $59 | $59 |
| Non-metallic whip | $72 | $72 |
| E Lite equipment pad | $172 | $172 |
| Parts total before wire and breaker | $3,721 | from $4,936 |
Add wire, a breaker and, where your town requires it, a licensed electrician for the circuit. Permits usually run $50 to $300. Breaker and wire size are in the manual for your size on the single zone manuals and multi-zone manuals pages.
Most of the extra money compared with a wall unit is in the indoor unit itself. A multi-zone wall air handler starts from $457, against $1,312 for the cassette.
Who should skip the ceiling cassette?
We would rather lose a cassette sale than sell one that doesn't fit the house. Skip it if:
- The room has a finished floor or living space directly above it.
- The ceiling is vaulted with no cavity, or shallower than the depth the manual lists.
- The room needs more than 18K. Cassettes stop there, and wall units go to 24K.
- Winters regularly drop below −13°F and the cassette would be your only heat. Like every line we sell, it heats down to −13°F, so keep a backup heat source and call us for cold-climate sizing.
- Getting into the attic is something you can't or won't do. Every cassette install needs work above the ceiling.
Next: What are the install steps for a ceiling cassette, start to finish?
What if your house is a little different?
What if my joists are 24 in apart?
MRCOOL's fit statement covers standard 16 in joists. For other spacing, read the hanging section of the installation manual and ask MRCOOL support at support.mrcool.com before you order.
What if I live near the coast?
The 5th Gen outdoor units have Gold Fin corrosion coating on the coil, which helps in salt air. Place the outdoor unit out of direct salt spray when you can.
What if I want cassettes in some rooms and wall units in others?
That is a common multi-zone plan. Confirm your exact combination on the multi-zone spec page before ordering. Our cassette multi-zone planning guide walks through layouts room by room.
What if a room is long and narrow?
Because the cassette blows one way, place it near one end of the room with the outlet facing down the length, the same way you would aim a wall unit.
What should you do next?
Check the attic above each room you have in mind and note the joist spacing. Then size each room and decide between the 18K single zone and cassette rooms on a multi-zone.
When you have room sizes, call us at +1 (844) 999-9725, Monday to Friday, 9 AM to 5 PM EST, or text 302-385-6142, and we'll help you pick the cassette size and outdoor unit. Shipping is free to the 48 contiguous states, and orders leave our Kentucky warehouse in 2 to 4 business days after the order is verified.
