If you are trying to cool a kitchen of any size, an area that receives full sun, or a room that's larger than 300 square feet (which is about 15 feet by 20 feet), you need the power of a large in-wall or window air conditioner. That means a minimum rating of 9,000 BTU, a beefy compressor that blasts a sufficient amount of icy air and a fan that can circulate it through the entire space. Be careful stepping up too much, however, a unit more powerful than 12,000 BTU will require a 230-volt outlet, which means you'll probably need to call an electrician.
Among air conditioners in this size category, we found the best consensus among experts for the LG LW1216ER (Est. $350) . This Energy-Star Qualified, 12,000 BTU unit is about as powerful an air conditioner as you can find that will run on 115V AC and not require a dedicated 230-volt line, and it can handle a room of up to 550 square feet. The small remote control lacks a display, but is otherwise full-featured and lets you control all functions, including temperature settings, from across the room.
The LG LW1216ER is a top pick across the board in professional tests. At TheSweethome.com, Liam McCabe recommends it for a larger room after testing its smaller sibling the 8,000 BTU LG LW8016ER ($240). ConsumerReports.org's Mary H.J. Farrell notes that the LG LW1216ER was one of the top models in its size class in the site's most recent round of testing, and that it was also designated as a Best Buy.
Because the LG LW1216ER is a new-for-2016 model (the 16 stands for the year it was released), it has virtually no owner feedback yet. However, its predecessor version, the LG LW1215ER (Est. $350) is identical with the exception of the Energy Star Certification (it lost that designation after the U.S. Department of Energy updated its energy efficiency ratings in late 2015), has plenty of feedback and we can certainly extrapolate the anticipated performance of the LG LW1216ER based on reviews of the LW1215ER. Those reviews are universally laudatory when it comes to cooling a room quickly and efficiently.
We did see complaints about the LG LW1215ER, however, and, as with the positive comments, we can apply those to the LW1216ER as well. Those cons include a difficult install process (most definitely plan to have an assistant or two), units arriving damaged at the owner's home, and poor customer service from LG in response to breakage within the warranty period. And, as with all air conditioners, noise gets a lot of negative press. You can probably expect that to be an even bigger issue with the LW1216ER, because the more energy efficient a window air conditioner is, the louder it is perceived to be.
The bottom line is this: If energy efficiency is your top priority, get the LG LW1216ER. If quiet operation is a top priority (which it may be if you're putting this unit in a bedroom or meeting room), get the LG LW1215ER -- if you can find it, that is, its availability is somewhat limited.
If you prefer something with a few more bells and whistles, our Best Reviewed room air conditioner from last year, the Frigidaire FFRE1033Q1 (Est. $300) is still available and still worth a look. It fell from our top spot this year because it did quite poorly in the one independent test we saw (which is odd, because it did pretty well last year in the same testing protocol). However, it's one of the top picks in a roundup at Popular Mechanics, with Heidi Davis saying it's simple to install, and that she likes the thermostat-equipped remote control, which "allows you to see, set and maintain room temperature without having to get up."
Owners also love the Frigidaire FFRE1033Q1; so much so that, if we rated strictly on positive owner reviews, this Frigidaire room air conditioner would still be our pick. The only real complaint we saw was that the materials seem cheap, otherwise, it's reported as easy to install, simple to use, and cools a room quickly and well. Many also note that it's very quiet and many say they installed it in a bedroom and the low hum is barely noticeable.
The Frigidaire FFRE1033Q1 lost its Energy Star Certification this year due to new regulations (requiring an EER of at least 12 for that designation), but it's still very efficient with an EER of 11.3. It's also more feature-rich than the LG models we discuss above, including a sleep mode, temperature sensing remote, and an ionizing air filter to reduce allergens in the air. While the air filter is not tested in professional roundups, owners love it.
The Frigidaire FFRE1033Q1 has slightly less cooling capacity than the LG -- it's rated at 10,000 BTU, which is appropriate for a room of up to 450 square feet. To keep humidity in check, it's also capable of removing as much as 3 pints of moisture from the air per hour.
Finding an in-wall air conditioner to recommend proved to be a tall order. We couldn't find a reputable expert review of any current model, and even user reviews are largely hard to come by. That said, we did see higher than average feedback, and higher than average ratings, for the Koldfront WTC12001W (Est. $520). This 12,000 BTU air conditioner is designed to exclusively mount through the wall and cannot be installed in a window. It has an EER of 9.5 so it is not Energy Star Certified. It can cool rooms up to 550 square feet and is a dual-function unit that can also heat a room of up to 450 square feet. Owners say it's easy to install, but, unless you already have a dedicated 220-volt outlet, you'll need to hire an electrician to install a new line.