You’ve seen the videos…at least if you live in the north. They’re called Polar Bear Clubs and they take an annual dunk into freezing winter water called the Polar Bear Plunge. All you need to join is thick skin and maybe drink a quart of Kraken Rum.
But no matter how thick your skin or how much Kraken Rum you drink (especially given how much rum you drink), there are times of year in the north when it gets hot. Maybe not Georgia/front-porch-of-the-sun-hot, but hot nonetheless. And you’ll need (or desperately want) air conditioning.
Depending on the area of the country you live in, the phrase ‘air conditioner’ means different things. In hot climates, it’s that controller on the wall that makes the room not hot. In colder, northern climates it means the annual trip to the garage or basement to haul out the window mount air conditioner. While it may not be cost effective to use multiple window units in a heating climate, they do make sense for smaller apartments or states like Maine which have short but definite cooling seasons.
What is a Window Air Conditioner
And I promise I won’t answer ‘an air conditioner in a window.’ A window air conditioner is a self-contained unit, unlike a split system. All the elements of the air conditioner, the evaporator, condenser, expansion and compression valves, pumps and fans are contained in one box. See this post for the actual air conditioning mechanics.
The window air conditioner pulls warmer air from the living space, circulates it over the cooling coils, and blows it back into the room. The heat is dispersed to the exterior.
Though they are called window air conditioners, they can be installed through the wall as well. This requires that a properly sized hole is hacked into the side of your house, framed and flashed for water detailing. There are also different installations for double hung, casement, sliding or awning windows.
Ease of Installation – Kind of an obvious advantage. Drive to the Big Box store, whip out your credit card, drive home, unbox it, pop it in the window, and plug it in. Maybe I shouldn’t be celebrating how easy it is to install the electrical hog but … it is quite easy.
Cost of Installation – Like ease of installation, cost is something with a seemingly obvious answer. The little window units must be less expensive than a big central system. And depending on the climate, this may or may not be true.
Very hot climates that require cooling year-round lean toward central air systems. Installing window A/Cs in every room is expensive upfront and more expensive to operate. A central system exploits large scale economy to more cost effectively cool entire buildings.
To manage equivalent cooling on a large building would require several if not dozens of single window units. The cost would be very high, having to purchase so many self-contained units in lieu of a single larger one.
Now move that to a northern climate that only needs cooling part of the year. A window air conditioner may only be installed in one or two windows and only run for a few months. In this case, the purchase of a single small unit is much, much less expensive.
Cost of Operation – Cost of operation mirrors the installation situation. Cooling an entire building year-round in a hot climate is much cheaper with a single large system. In northern climates, where cooling is only needed for a month or two, efficiently targeting cooling to a single room (and a single window unit) is much more efficient.
Efficiency – Energy Star has efficiency standards for louvered and non-louvered vent window air conditioners of at least a 9.7 EER (energy efficient ratio). This is dramatically better than in decades past but still suffers in comparison to the large scale efficiencies of central air systems. The highest rated Energy Star central system for 2011 had an EER of 25.5.
Cooling Capacity and Space– A window mounted air conditioner’s BTU cooling output should match the space it is cooling. Here’s a simple sizing chart for room size. This isn’t exact and there are many adjusting factors like having heavy shade, heavy sun, many incandescent lights, if the room is a kitchen (the oven), etc.
Obviously there are limits to how large a space can be cooled by a window installed unit. Central systems have no such limitation and can be scaled up to cool any size building.
Noise – An under-reported disadvantage (or under-reported until you’ve installed it) of a window unit is noise levels. Window units contain all the mechanical elements in a box sitting in your window. The compressor, condenser, evaporator, fans etc. are all sitting in your window, cranking away.
Some folks find the noise soothing and helps with sleep, but most fall on the other side of this thought. The central system, with all the mechanical stuff … elsewhere is much quieter.
Controls – Lastly, the temperature, fan speed, and other controls tend to be less sophisticated on window air conditioners. Or rather sophisticated controls are more expensive relative to the cooling load handled. Partly a function of space and partly of cost, central air systems tend to have more robust control options.
Zoning – Being able to cool just one room is the easiest way to save electricity. Window mounted models have an obvious advantage since it’s a simple matter of turning off that room’s AC.
There are a number of other minor features like the ability to direct air flow, ‘Power Saver’ efficiency settings, the fact that air conditions act as minor league dehumidifiers and fresh air intakes. All of these can be considered when shipping for your window-based electric conditioner.