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How to Improve Your AC Results by Knowing the BTU for a Room Size

Window AC in window

Understanding air conditioners and how they're rated can be a challenge. To the average consumer an air conditioning unit looks like a metal or plastic box that blows cold air out of the front or sides. Most consumers make the mistake of confusing the importance of watts versus the importance of BTUs.

There is a difference and it's important to understand what the difference is so you can cool your home properly. Simple wattage is not an accurate indicator of how effective an AC is.

If you want to know how much power is needed to run an AC, look at the watts, voltage, and amperage. These are measurements of power usage. Air conditioners are rated by how much heat they can remove from a space per hour. Their cooling power measured by BTUs or British Thermal Units. It's a scientific measurement of how much energy is required to cool a single pound of water by one degree Fahrenheit.

Typically the BTU measurement is located on the air conditioner, along with other information, on the side or back of the unit. Usually the BTU on the unit is a measurement of BTU/hour. The higher the number of BTUs, the stronger the cooling power. For this reason, many consumers believe it better to buy an AC with a higher BTU rating. However, it's important to consider efficiency and comfort over excessive power.

If you purchase a unit with the highest possible BTU rating, it may actually cause the unit to operate inefficiently. That's why the BTU for a room size is so important. If an air conditioners' BTU rating is too high for the room, it might waste energy cooling it beyond its capacity before it shuts off. If the unit is undersized, it will have to work too hard to cool off the space and keep you comfortable, thus costing way too much money to run.

Measuring tape

The best way to measure your room for the best possible results is to multiply the length, width, and height of the room. This provides you with proper guideline needed to determine how much BTU is required.

Depending on room conditions, you might want to increase the BTU rating. How many windows are in the room and whether or not the room is insulated are important factors to consider, too. However, normally, the size of the room is the best indicator of how much BTU you need. provides the following basic guideline for room sizing.

  • 5,000 BTUs cools up to 150 sq. ft.
  • 8,000 BTUs cools up to 350 sq. ft.
  • 10,000 BTUs cools up to 450 sq. ft.
  • 12,000 BTUs cools up to 550 sq. ft.
  • 14,000 BTUs cools up to 700 sq. ft.

Air conditioners remove both heat and humidity from the room. If the unit is not properly sized it will cool the room quickly but only remove some humidity. A properly sized AC will remove humidity effectively as it cools.

  • Before making your purchase, make adjustments for the following circumstances:
  • Reduce the capacity by 10% if the room is heavily shaded
  • Increase the capacity by 10% if sunny
  • Increase capacity by 4,000 BTUs if the unit will be in the kitchen
  • Increase capacity by 600 BTUs if more than two  people occupy the room
AC installation

Once you've sized and installed your AC maintain it properly for the best possible results.

Did you know that heating and cooling comprise 40% of the average citizen's energy consumption? To reduce electrical bills and increase efficiency follow the simple guide below.

  • One of the biggest problems with efficiency is improper use. Make sure your windows and doors are closed when operating your unit.
  • Another factor is poor installation, faulty service procedures, and inadequate maintenance.
  • It's important to keep the unit clean. Clean filters at least once a month. Change them as indicated by the manufacturer.
  • Be sure that ventilation fins are open properly.
  • Increase the thermostat at night or when you're not home so it doesn't run excessively. This keeps energy use down.
  • Use ceiling fans to help distribute cooler air.
  • Ventilate the attic. A cooler attic can help lower the internal temperature of the house by as much as 10 degrees.
  • Following this brief guide will make improving AC results easy.

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