I just moved into a new apartment and they have a 25"x 15" pre-built wall sleeve for a wall AC unit. Not knowing the difference, I purchased the extravagantly less expensive window AC unit that has exhausts on the side and on the back. Realizing this, I figured that (with some internet searching) the unit may heat up because it isn't exhausting properly. If I have 1" on each side of the AC in the wall sleeve, is it good enough for exhaustive purposes? Also, what would you do for affordable cooling on a first floor apartment with a 750 ft^2, 2 BR, apartment? You should check the manual that came with the AC, it might tell you minimum clearances. My window AC unit only says: Side louvers and the rear of the air conditioner must have clear air space to allow enough airflow through the condenser, for heat removal. I would say that 1" does not meet that requirement, particularly if the sides of the sleeve extend out past the end of the AC. You didn't directly ask about the difference between the window units and the thru-wall models, but I agree with @Vitality that the price jump probably has a lot to do with the size of the unit.

If you're trying to cool 750 ft^2 you're going to want to get a bigger unit than the $99 budget models they sell at Walmart. According to this Energy Star chart, you'll need a unit with around 18,000 BTUs/hr of cooling. If you get a unit that's too small it will just run and run but not cool or dehumidify the apartment, wasting you money. Plus it will probably burn out the compressor faster since it's not getting a break. How To Cool An Apartment Besides the AC, here are things that can help you keep the apartment cool: Get curtains and close them during the day, especially if you're not home. Lots of heat enters the house as solar radiation and you can prevent it if you keep the light out. If you're on a budget, Home Depot et al sell blackout roller blinds that are pretty reasonable. Switch your light bulbs to LEDs (or CFL, if your budget requires... but spring for the LEDs if you can, they're better and will save you money). A 100 watt incandescent light bulb puts out almost 350 BTUs/hr in heat.

If you have a bunch of those on, that's going to really going to add up. If the temperature is cool at night, fans in the window can help exhaust hot air and bring in cool air from outside. I'm not a big fan of fans just circulating air inside, like ceiling fans and tower fans, since they don't actually cool the air. But some people like to feel the breeze. Definitely shut those fans off when you leave otherwise you're just wasting electricity and heating up the room. Use the stovetop exhaust fan when you're cooking. It will remove the hot, humid air. Same thing for exhaust vents in the bathroom during/after a shower. Basically anything else that reduces your electrical usage will also reduce heat in the apartment. E.g. I like to put my rice cooker on the porch even if I'm not eating outside. I'd say that if the wall is projecting in front of any more than 1 inch width of the side exhausts, you do not have enough clearance for proper operation. You could actually mount your window A/C in a window is about the only affordable option.

Honestly, unless you have lots of windows or A/C is not that important, you are going to need to spring for a proper wall unit. I might be wrong but every single window AC i have ever seen has fins on the back and that's where the heat is exhausted. single room air conditioning units reviewsMoreover, I suspect there's really no difference between the wall and window mount acs. boat ac units for saleThe wall ones might be pricier because they are usually more powerful as they are intended to cool bigger space. air conditioning outside unit fanBut inside those units are identical.Don't let the initial low cost of an off-the-shelf window-sized air conditioner fool you. Before long, you'll be paying far more for that cool air than you would with an alternative such as geothermal.

That back bedroom is just too hot! Maybe “they” didn't run a big enough duct, or you’ve never had AC there.Window-sized air conditioners may seem like a good deal, but they're woefully poor users of energy.It doesn’t matter if you’re in a four room apartment or a single family home, the weather outside is hot. The first stop for most people is the home improvement store, Amazon, or whatever else is available in a moment of desperation. We purchase a $200 window or "through-the-wall" air-conditioning unit, and pay tremendously high energy bills for a woefully inefficient product. Let's look at some of the real and intangible factors with regard to the cost of installing a window air conditioner, some of which may not have come to mind. A through-the-wall air conditioner is typically chosen in response to the following question: “What is the largest number of BTUs I can get for the least expense?” Here a short list of things that may be wrong with this line of thinking:

The window AC is likely either oversized or undersized for the space, each of which wastes energy A through-the-wall air conditioner is likely rated for an EER (energy efficiency rating) of 10. The #1 bestselling window AC on Amazon is a Frigidaire FRA052XT7 5,000-BTU Mini Window Air Conditioner, with a 9.7 EER. The cost is $119.73.  As I stated earlier, we buy “cheap” in a pinch; Not really …there’s more… If you’re shopping for high efficiency window units, the next best option is the Friedrich SQ05N10B 5,200 BTU - ENERGY STAR - 115 volt - 11.2 EER. Still, a long way to go to measure up to the minimum standards of 13 SEER for home air conditioners, and they’re getting pricey at $578.94 on Amazon. Installation rarely works out the way instruction show, and the finished product is typically considered, even by the installer/homeowner as "poor at best".  This results in increased thermal gains due to infiltration of air, solar gains, and other losses in efficiency. 

The install may even be a safety hazard. One report in 2011 states that Poorly Installed AC Units Cost New York City $180 Million in Fuel Consumption each year and the New York Times reported in a similar article that it was found that the average gap size for an AC unit was about the size of a fist, and “The cost of fuel lost to such energy waste is equal to the total cost of cooling the building alone…”. I have visited many homes and businesses over the last 30 years in which they've installed a window air conditioner(s) and complained of increases in energy expenditures of $50-$200 per month. Many of these homes could be completely conditioned with geothermal HVAC systems for fraction of that kind of energy cost. Beyond all of this, first cost is so low for the installation of window air conditioning units that it has become epidemic in many areas, even being used in office buildings and residential apartments. Now, let’s continue the list of adverse results from these unsightly pimples, commonly called window air-conditioners. 

Window air-conditioners can result in: Proportionally high CO2 emissions Increased noise pollution proportional to the number of window ACs in a building Increased safety risks and equipment hazards on ground level (and even upper level) installations A greater security risk (often because of poor installation) Below is a chart depicting energy consumption of the typical 1500 ft.² house using window air-conditioners (10 SEER), and conversely using a geothermal HVAC system (20 to 40 EER). To be fair, it's not uncommon for a home that uses only through-the-wall air-conditioning to use less energy per square foot than a home that uses central air-conditioning. This has to do with energy habits. We've all been in homes where the occupants only air-condition the living room during the day and then just the bedroom at night. This is a good energy habit, and can also be effectively applied with HVAC (ducted) systems using zoning (a well installed duct system with automatic dampers to cool and heat only the rooms occupied).

Much like energy efficiency in vehicles, we often feel we can't afford the costs associated with high efficiency products, when in reality the economics show a much different picture. It’s hot out there. Take a moment and “look before you leap”.  Grab a cool drink and consider the resources available.  You’ll make the right decision when you “Think Green”. Geothermal Cooling and Heating; Sharing Energy with Mother Earth Jay Egg is a geothermal consultant, writer, and the owner of EggGeothermal. He has co-authored two textbooks on geothermal HVAC systems published by McGraw-Hill Professional. © 2016, Green Builder Media. This article is the exclusive property of Green Builder Media. If you would like to reprint this content, you are free to extract a short excerpt (no more than 1/4th of the total article), as long as you 1. credit the author, and 2. include a live link back to the original post on our site. Please contact a member of our editorial staff if you need more information.