Wednesday, August 25, 2010
BTUs and Your Air Conditioner
A British Thermal Unit -- or BTU -- is the measure of an air conditioner’s power output and cooling capability. Normal BTU range for most air conditioners goes from around 5000 for a small window unit to 30,000 or more for a central AC system. BTU output is directly related to the size and cost of a unit—lower BTU means less power and lower cost, higher BTU means more power and higher cost. When you’re shopping for a new air conditioner, pay special attention to BTU because this is the best indicator of whether the unit is powerful enough to meet your needs.
What is a BTU?
If you’re talking about air conditioners, BTU describes the power capacity of a specific unit. Generally, BTU output corresponds to the size of the space an AC can cool—a unit with more BTU can cool a larger room. About 20 BTUs are needed for each square foot of space in a room or home. Other things to consider are the height of ceilings, size and number of windows, and amount of insulation.
Still, BTU is a fairly accurate indicator of cooling capability, though it usually makes sense to adjust down. For example, if your living room is 10 feet by 15 feet and has a total area of 150 square feet, you’d multiply that by 20 BTUs to get 3000. Therefore, you’d need an air conditioner with at least 3000 BTUs to effectively cool your living room. However, when you take into account the other factors that impact the space—like cathedral ceilings, large windows, or an unusually warm climate—you may find that 3000 BTUs are not enough to keep you cool. In that case, it’s obviously best to choose a unit with higher BTU.
There’s a wide range of BTU outputs available in both commercial and residential air conditioners. Most residential units average 5000 to 30,000 BTUs. 12,000 BTUs equals one ton of air; some units are marked with a measurement in tons rather than BTU. A “2-ton” AC, for instance, means that the unit has an output of 24,000 BTUs.
Portable air conditioners average about 5000 to 12,000 BTUs. Wall and window units can reach upwards of 24,000 BTUs at the high end. Mini split systems range from 9000 to 24,000 BTUs, while multi-split systems and central air conditioners can put out 30,000 BTUs or more. Industrial air conditioning systems frequently have BTU output significantly higher than 30,000.
Not only will BTU tell you how much room an air conditioner can cool, but it can also give you an idea of how much you’ll have to pay to run it. The more BTUs a unit uses, the more it will cost to operate. To save money on utilities, look for air conditioners with a high Seasonal Energy Efficiency Rating (or SEER). Additional features like programmable thermostats, timers, fans, and power-saving settings can reduce strain on your system, boost efficiency, and lower your energy costs while still keeping your home cool.
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