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Swamp Cooler vs Window Air Conditioner
See also: Swamp Coolers - Evaporative Coolers
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Although swamp coolers and air conditioners were invented to turn hot air
into cool, the science behind each method is quite different.

I think everyone is familiar with the workings of a window air conditioner, but if
you're a little fuzzy on how a swamp cooler operates, here is a very brief
description.

What is a swamp cooler? It’s just another name for an evaporative cooler.
Water is used to wet absorptive pads around the sides of the cooler.

A fan or "squirrel cage" draws outside air through the pads and the air is cooled
as the water in the pads evaporates.

The major benefit of this type of cooler is that you only need to power a water
pump and a fan to draw the air through the coolong pads.

They typically use between three and 10 gallons of water per day. That's
equivalent to a few toilet flushes or
a short shower.

Swamp coolers are effective only when the relative humidity is below 40%. They
work well in the Southwest, West Texas, and parts of Idaho, Washington,
Colorado, Wyoming, and Montana. In these areas you could expect a swamp
cooler to achieve a 15 - 25 degree difference between outside and inside
temperatures.

Air conditioning, on the other hand, is popular because it will reliably dehumidify
and cool the air, no matter where you live.

However, unlike an air conditioner that recirculates the same air, a swamp
cooler is continually replacing the air inside the structure which makes it ideal
for uninsulated buildings such as workshops and garages.

For the sake of comparison in this article we'll use a medium size, 1,400 square
foot single story home. This is the largest sized home, in terms of square feet,
that a single window air conditioner could reasonably be expected to cool.

A home of this size would require a 24,000 BTU window unit. Cooling the same
amount of space with a swamp cooler would require a unit with a capacity of
4,500 CFM.

The cost of a swamp cooler vs an air conditioner
The price of an air conditioner or swamp cooler is determined by its cooling
power. For air conditioners it's measured in BTUs; for swamp coolers it's
determined by the number of cubic feet per minute (CFM) of air it displaces. The
higher the number of BTUs or CFM, the more expensive the unit.
Which is cheaper to operate?
As far as power consumption goes, the swamp cooler wins this one handily. A
4,500 CFM swamp cooler consumes slightly less than 900 watts. At $0.11 per
kWh (2011 national average), the swamp cooler costs $0.10 per hour to run.

A 24K BTU air conditioner, on the other hand, consumes around 2,700 watts.
At $0.11 per kWh the cost is $0.30 per hour to operate - or 3 times as much
as the swamp cooler.

Annual operating cost
Based on Energy Star's estimate of 750 hours of use per year, the air
conditioner would cost $225 a year to operate, versus $75 for the swamp
cooler.

Installation comparison
Window air conditioner:
A 24,000 BTU unit runs on 230 volts (12 amps)
which requires the installation of a separate outlet for the AC. A lot of factors
come into play when determining the cost but figure on around $250.

Once the outlet is installed all you need to do is strap on your hernia belt, hoist
all 130 pounds of it into the window opening, attach a couple of support
brackets to the outside wall and plug it in.

Swamp cooler: Installing a swamp cooler could run anywhere from less than
$100 to an amount equal to the cost of the unit itself depending on the
installation placement (ground or roof) and whether or not you hire a
contractor to do the installation for you.

A swamp cooler installation is more complex than a window AC installation
because it requires a water supply and duct work fabrication in addition to
connecting it to a power supply.

The cheapest and easiest method of installation is mounting the cooler at
ground level and ducting the cooled air into the building through an outside
wall. Once the unit is wired up you can use a special two way outdoor faucet
fitting to supply the water or tap into an existing cold water line with a saddle
clamp.

You'll also need to fabricate the duct that runs between the cooler and the
building and purchase a grate or diffuser to cover the duct where it meets the
interior wall.

The second installation option is mounting it on the roof. In one respect this
makes a lot of sense because you can locate the supply duct at the most
efficient distribution point in the building and take advantage of the fact that
cold air falls. But you'll also incur the additional expense of extending the
supply duct down through the attic and hiring a small crane to lift the 400
pound unit into place.

Another possible drawback is that you, or someone else, has to climb up on
the roof a couple of times a year to perform routine maintenance.

A swamp cooler can also be wired for 220 volts to minimize the voltage drop
(power loss) if the unit
is located beyond a reasonable distance from the
power source.

Maintenance
Maintenance is not really an issue with a window air conditioner other than
rinsing off the filter once in a while.

A swamp cooler needs to have the belt tightened, the motor oiled, pads
replaced, and the water reservoir cleaned on a regular basis to maintain
operational efficiency as well as the health of the building's occupants.

Swamp Cooler vs Window Air Conditioner: And the winner is...

Price: It's a draw
The purchase price for either appliance in the 1,400 sq ft
cooling capacity category is basically the same.

Installation: Window air conditioner In terms of cost and simplicity of
installation the window air conditioner has a slight advantage.

Maintenance: Window air conditioner For the reasons just stated above.

Cost to run: Swamp cooler This one isn't even close with the air conditioner
costing 3 times more to operate than the swamp cooler.

Bottom line:
Swamp cooler:
If you own a small to medium sized home where the climate is
consistently dry and you plan on living there for 5-10 years you'll save money
in the long run with a swamp cooler.

Window air conditioner: If you expect to be moving in a few years you're
better off with a window air conditioner because it's less expensive overall in
the short term and you can take it with you on moving day.

Toss up: If you live where the climate is predominately dry but with periods of
humid weather (rainy season) you have to weigh the trade off between long
term energy savings and the temporary discomfort you'll experience when the
swamp cooler is ineffective.
Roof mounted swamp cooler
Both types of coolers have appropriately
sized models available for $600 - $800  
making the cost to purchase nearly
identical.

Sizing note
AC:
Figure on 18 - 25 BTU per square
foot.

Swamp cooler: Optimal CFM = 3 to 4  
times square footage.
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