What you need to know before buying a Window AirConditioner

Late last summer we bought a newhouse and for the first time in about adecade, didn't have central airconditioning. In my opinion, having acool place to sleep at night is anabsolute necessity. I have reached thispoint in my life after having spent one-too-many nights in my 20's sleepingunder a wet towel. At that time, wewere unable to afford central airconditioning and our condo associationprohibited window A/C's because oftheir poor aesthetic. This is all to saythat I have been considering my A/Coptions as the summer approaches andhave now made my purchase. I

learned a few things that I want to pass along.Â

As a college student in the late 1980's, I spent my summers working as an assistant for anHVAC (Heating, Ventilation and Air Conditioning) company. Armed with substantially outdatedknowledge, I set out to buy a new central air conditioner. After speaking with 3 local HVACcompany's, it seemed like the preferred solution was to install a new heat pump that would cool thehouse in the summer. Unfortunately, the $8,000-$12,000 price tag made this option a completenon-starter. When I am ready to replace my 4-year-old furnace, I will consider going this route,but in the mean time, it does not make a lot of sense. They could sell me just the central air unit,but the economics were almost as bad (ie. $5k for something that we would use 2 months out of theyear).

At this point, I moved onto Plan B - finding a portable A/C unit.

Before getting into the specifics of what I was looking for, some definitions are in order:

BTU (British Thermal Units or BTU/hour) - you will have heard this term in connectionwith your barbeque or furnace as a BTU is a measure of heat per hour. For A/C units, youare trying to rid your room of warmth and therefore you need just enough BTU's offset your home'snatural capacity to generate and store heat. Every home is different as the size of the room, thequality of insulation, amount of direct sunlight and whether the room has a heat source (ie kitchenstove) all factor into the calculation. Far too many people think bigger is better when it comesto BTU, but this is dead wrong.  If you buy a unit that is over-sized, it will cycle on and off tooquickly, which boosts your operating costs and cause wear and tear on the compressor. Theoptimal BTU depends on the size of the room you are trying to cool. A quick rule of thumb - takethe square footage of your room (length x width) and multiply by 25. If your master bedroom is

24x20, you would need 12,000 BTU's to efficiently cool your space. As an aside, 12,000 BTU is alsoknown as '1 ton' as this is the amount of heat required to melt a 1 ton block of ice in 24 hours. Ifyou want to be a little more accurate with calculating your optimal BTU's, this link provides a good

calculator.

SEER (Seasonal Energy Efficiency Ratio) - This ratio is shown on your new A/C's "Energyguide"label and represents the cooling output per watt of electricity. In this case, bigger is better as ahigher number indicates better efficiency. This ratio can be used to estimate the annual electricalcost (the industry assumes 1,000 hours of usage per year) by taking the A/C's BTU and dividing bythe SEER, then taking the product and multiplying by the average cost per kilowatt-hour ($0.12in the US in 2011). If the label to the right was for a 10,000 BTU A/C, the annualelectrical cost would be $90.23/yr (or $0.09/hour). If you are buying your unit used, use thewattage shown on the model plate as the annual consumption, then multiply this number times$0.12.

In determining which portable A/C I wanted to buy, I determined that I needed a 10,000 BTU unitfor my master bedroom.  I then did Google and Amazon searches to find models that were wellreviewed (based on noise, features, looks, etc), then narrowed the field down to 2 for a final analysis.  My short list looked as follows:

Manufacturer:

LG

Frigidaire

Model:

LW1012ER

FRA106CV1

Â

BTU:

10,000

10,000

SEER:

10.8

 10.8

Cost @ Amazon:

$279.00

$259.00

Annual Energy Cost

(BTU/SEER * $0.12):

$111.11

 $111.11

Given that I would have been happy with either unit, I bought the Frigidaire as it has thelowest overall cost. Had the annual energy costs been different, I would have compared the 'all-in' cost over a 5 year time horizon.Â

I have been very happy with my purchase and have been sleeping soundly ever since.