The MRCOOL 5th Gen DIY 18K BTU Single Zone Mini-Split handles a bigger single space — a finished basement, a great room, or an addition with high ceilings — built for 700 to 1,000 square feet, comfortably.
A traditional mini-split this size usually means hiring a licensed HVAC contractor to run refrigerant lines and pull a vacuum on the system before it's legally allowed to run — a step that means scheduling a visit, paying for labor, and working around someone else's calendar. This system skips that step. The line set arrives pre-charged with refrigerant from the factory, so there's nothing to vacuum and no license required to connect it, which typically saves a few thousand dollars in labor costs and lets you install it on your own timeline. It's not just marketed as DIY-friendly, either — this is the only ductless system on the market with a U.S. patent specifically covering this pre-charged installation method (Patent No. 11,125,479).
It runs on 230V power, a step up from the 115V used by the smaller units in this line. Most homes already have a 230V circuit available (the kind that runs a dryer or electric range), so it's usually just a matter of confirming you have one near the install site.
Installation is still homeowner-work: the 25-foot line set comes pre-charged with refrigerant, so there's no vacuum pump, and you're not opening walls or running new ductwork. The pre-charged line set fittings are Intertek-tested and certified, which is part of why the vacuum-free setup holds up to full safety standards. Controls are the same across the line — remote, the MRCOOL app, or Alexa and Google Assistant — with the same temperature-tracking sensor built into the remote. If the power goes out, the system comes back on with your previous settings and vent position already dialed in, instead of resetting from scratch.
This unit is rated to keep heating down to about 5°F outside and runs around 58 decibels, close to normal conversation, even at this size, all at a 22.5 SEER2 efficiency rating.
Registering the MRCOOL DIY 18K BTU Mini-Split gets you 5 years of parts coverage and 7 years on the compressor.
