Although swamp coolers and
air conditioners were invented
to turn hot air into cool, the
science behind each method is
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
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, on the high end, 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
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.
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
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 needs to be located beyond a reasonable distance from the power source.
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.
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
Both types of coolers have appropriately
sized models available for $600 - $800
making the cost to purchase nearly identical.
AC: Figure on 18 - 25 BTU per square foot.
Swamp cooler: Optimal CFM = 3 to 4 times