What is the best air conditioner for a 150 sq ft room?
A 150 sq ft small bedroom or office has a specific cooling need. Undersize it and the unit runs flat out without ever cooling; oversize it and it short-cycles and leaves the room humid. These are the real units whose coverage matches a 150 sq ft room, sized by our own rule and ranked by how closely they fit.
The short answer
For a 150 sq ft room, the closest match we list is the Amana 5,000 BTU Window Air Conditioner w/ Mechanical Controls, a window unit that covers up to 150 sq ft at 50 dB(A), in stock at Sylvane for $189.99.
Prices last refreshed Sep 24, 2026Independent, nobody pays for placement.
We size every unit to a 150 sq ft room using the ENERGY STAR room air conditioner sizing chart, then rank by how closely each unit's stated (or cooling-power-estimated) coverage matches the room. Units that would be undersized are excluded. Buyable, fully-specced units break ties.
A common US rule of thumb for a standard, reasonably insulated room with an 8-foot ceiling is about 20 BTU per hour per square foot, so a 300 sq ft room is often quoted around 6,000 BTU and a 500 sq ft room around 10,000 BTU. compare.ac instead sizes against the official ENERGY STAR room air conditioner chart, which is not a flat rate: it recommends about 7,000 BTU for that same 300 sq ft room and about 12,000 BTU for a 500 sq ft room, then adjusts up for a hot or humid climate and down for a mild one once you pick your region. Add capacity for a sunny west-facing or top-floor room, a kitchen, or extra people who are regularly in it. Undersizing means the unit runs flat out and never cools; oversizing short-cycles and leaves the room cool but clammy.
Does my climate change how much cooling I need?
Yes, more than almost anything except the size of the room. compare.ac's base sizing, before any climate adjustment, follows the official ENERGY STAR room air conditioner chart, which assumes a temperate summer. A hot, dry region like Arizona, or a hot, humid one like Florida and the Texas Gulf coast, realistically needs on the order of 20 to 30 percent more cooling per square foot, because the outdoor design temperature is higher and, in humid places, the unit also spends energy removing moisture (the latent load). A mild, marine climate such as the Pacific Northwest or coastal New England needs a little less. compare.ac applies this adjustment once you pick your region in the tool, using ASHRAE Standard 169 design temperatures and ACCA Manual-J regional sizing practice, and always shows both your real room size and the adjusted figure it sizes against. For a final purchase, a professional Manual-J load calculation for your specific home is the accurate method.
How much noise is acceptable?
Noise is measured in dB(A). A quiet split indoor unit on a low setting can be around 19 to 25 dB(A), which is barely audible and fine for a bedroom. Around 30 to 35 dB(A) is a soft hum that most people accept in a living room. Portable monobloc units are usually 52 to 58 dB(A) because the compressor sits in the room with you, which is closer to a dishwasher and can disturb sleep. If quiet matters, a split almost always wins; if you only cool occasionally, a portable may be acceptable.
Do I need a professional installer?
For a split or multi-split, yes. There is no US law banning DIY installation as such, but under EPA Section 608 only a certified technician may open the refrigerant circuit, and the EPA states plainly that this includes connecting or disconnecting the pre-charged line sets sold with “DIY” mini-split kits. That is worth knowing, because it is the opposite of how those kits are usually marketed. Doing the refrigerant work yourself voids the manufacturer warranty and risks a dangerous, illegal release. A portable monobloc, and most window units, need no installer at all: they are factory-sealed, so you set the unit down or fit it in the window and run the exhaust yourself.
