What Does BTU Stand For?

Proper sizing is essential for efficient air conditioning. You should base your cooling needs on the square footage of your room or entire living space that you want to cool with air conditioning. You can figure the size of an area by measuring the length and width of your room in feet and then multiplying these numbers to calculate its square footage. Add up each room's square footage to determine your home's square footage.

Once you know the size of your area in square feet, you can reference the BTU chart below that breaks down the amount of cooling power needed to keep that space comfortable. The U.S Department of Energy (DOE) recommends 20 Btu per square foot of living space as a rule of thumb.

Designed by the Air Conditioning Contractors of America (ACCA), the Manual J Calculation is the most accurate method of determining how many BTUs are required to heat and cool your space. You can request a Manual J calculation from an experienced HVAC professional.

Your climate zone plays a significant role in determining the best air conditioning system to meet your home needs. If you live in a hotter climate, the difference between ambient air and your desired temperature will be more significant, so you'll need your air conditioner to work harder. Based on climate zones alone, central air conditioner units in Florida may need twice as many BTUs as in Maine.

Experts recommend a wide range between 30 and 60 BTUs of heat per square foot. The table below shows how many BTUs per square foot you’ll need for your home based on your climate zone.

Direct sunlight and the amount of shade your house receives are essential in cooling capacity. Direct sunlight will cause your air conditioner condenser to work harder due to the higher surrounding air temperature, consuming more BTUs. Add 10% to your BTU total for units in these locations.

Placing your condenser in a shadier area will result in greater efficiency, but it will also extend the life of your equipment. You can place shady trees and shrubbery around the outdoor unit, but consider that condensers also require good airflow for best efficiency. Ensure surrounding vegetation does not interfere with the condenser, blocking airflow into the unit and blocking it.

Insulation is essential to the cooling process. Living in a newer, well-insulated home may require fewer BTUs than an older house. On the other hand, an uninsulated home will need an air conditioner with a larger capacity to compensate for the loss of cool air through its walls. Thinner walls will cause your air conditioner to run longer to meet demand, leaving you with high energy bills.

If you are unsure of the insulation quality in your home, it's best to use generalized assumptions. A beach cottage built in the 1950s with no renovations should probably be classified as poor. A 5-year-old home inside a newly developed community deserves a higher rating.

Windows and doors don't provide the same insulation as insulation walls. If you have several doors or large windows in your room, size your BTU range by 10% to ensure it has sufficient cooling ability to keep up. It would help if you considered installing double-glazed windows or adding light-blocking and insulating curtains to increase your home's insulation.

A traditional ranch house will have more walls than a simple square house with the exact square footage, which means heat loss. A sprawling floorplan will need more capacity than a compact, two-story cottage. Modern homes with open floor plans will also require more power than those with smaller, enclosed rooms.

Units with higher BTUs are more powerful, but don’t automatically choose a unit with the highest BTU rating. An air conditioner’s BTU rating should match the square footage of the house to cool it effectively.

An air conditioner with too many BTUs will run for short amounts of time, turning on and off frequently. Not only does this waste energy and increase your energy bill, but the air conditioner also may not be able to cool the house entirely and adequately remove humidity if it runs for less time than it’s supposed to. Frequently turning on and off also causes more wear and tear on the unit.

An air conditioner with too few BTUs also wastes energy because it will run for long periods of time without sufficiently cooling the house. Again, your energy bills will be higher and additional strain will be placed on the AC unit.

BTU (British Thermal Units) is a unit for measuring energy transfer. An air conditioner’s BTU rating represents how much heat it can remove from a house in one hour. Simply put, BTUs tell you how powerful the unit is.

A kilowatt-hour (kWh) measures the energy needed to run an appliance for one hour. Power companies charge customers according to how much electricity they use per kilowatt-hour. By converting BTUs to kilowatt-hours, you can determine how much electricity an air conditioner will use and how it will impact your energy bill.

British Thermal Units Per Hour (BTUh) and tonnage (ton) represent an air conditioner's cooling capacity or how much heat your AC unit can absorb to reduce a room's temperature. One ton of cooling capacity converts to 12,000 BTUh.

Proper sizing is essential for efficient air conditioning. You should base your cooling needs on the square footage of your room or entire living space that you want to cool with air conditioning. Other factors to consider include ceiling height, climate zone, sun exposure, insulation, and home shape.