Even the most passionate fans of summer will concede that an air conditioner is a great addition to a home. When heat and humidity make it impossible to function, an air conditioner provides cool comfort in the bedroom, office, or family room. Air conditioners have come a long way in energy efficiency, but it’s still important to choose the right size for the job. Pronto’s Air Conditioner Buying Guide will give you the technical and feature information you need to get the best cooling with the least energy use. (Also see Pronto’s Portable Air Conditioner Buying Guide).
Modern air conditioners provide much greater energy efficiency and protection from coolant leakage than models made just 10 years ago. Look for digital controls and timer settings that maximize the balance between temperature and power consumption.
Match an air conditioner’s Btu/hr output to the square footage of the room you wish to cool. Look for a little more cooling power if you have ceilings higher than eight feet or if you’re cooling a south-facing room.
Window-mounted air conditioners are best for places with cold winters. Look for durable side stops that won’t crack or break over time. Check the windowsill you plan to use for signs of decay or weakness and be sure an electrical outlet is nearby, as air conditioner cords can be short.
Choose a wall-mounted air conditioner for more effective cooling in climates where you need to cool for six or more months each year. Installing a wall-mounted air conditioner requires structural changes to your home and should only be done by a professional builder.
Compare the EE ratings on air conditioners, which divide cooling power by wattage. Higher EE ratings equal greater energy efficiency. An air conditioner with the Energy Star uses 10% less power than a model without it.
A standard measurement of an air conditioner’s cooling power calculated in British Thermal Units (Btus) per Hour. One Btu is equal to the amount of cooling needed to lower the temperature of one pound of water by one degree.
Energy Efficiency rating, obtained by dividing an air conditioner’s Btus/hr by its wattage. Air conditioners with higher EE ratings need less power to cool.
An air conditioner that consumes 10% less power than similar models with the same features.
The flexible wings that extend from the left and right sides of a window-mounted air conditioner to block the space between its edges and the sides of a window.
An air conditioner that’s installed in a sleeve that projects through the outer wall of a home. These air conditioners provide better efficiency than window-mounted units but require professional installation.
An air conditioner that can be placed on a windowsill and is held in place by gravity and tension. Some of the largest window air conditioners may require an additional support rack that is bolted to the house beneath the window.
Air conditioners have a reputation for being environmental time bombs, in part for their energy consumption and in part for the coolants they use. Coolants are a necessity. An air conditioner works by pressurizing a refrigerant gas that absorbs room heat as it cools. The hot air is exhausted outdoors and the cold air gets blown into the room.
If you have an older air conditioner, it’s a good idea to replace it with a newer model. Stronger environmental regulations have led to better designs that prevent refrigerant gas from leaking and harming the environment.
Air conditioners have become better at managing energy consumption as well. Hard-to-read analog dials that you cranked all the way to the right for maximum cooling have been replaced by digital controls that let you set a precise temperature. Better air conditioners let you raise and lower the temperature during the day with automated timers and sleep settings. This last function lets you save energy while you sleep by automatically reducing cooling by a few degrees.
Energy-efficient features won’t do much if the air conditioner you choose is too large or too small for the room you use it in. An air conditioner that is too small will always be on trying to reach the right temperature, while one that’s too large will cycle on and off frequently, which draws more power than longer operation. The cooling power of air conditioners is measured in British Thermal Units (Btus) per hour. One Btu is equal to the cooling needed to lower the temperature of one pound of water by one degree. Matching the Btu/hr rating for an air conditioner to your room size will give you the most effective cooling. Grab a measuring tape and calculate the square footage of the room you wish to cool by measuring its width and length and multiplying these two numbers. Use the chart below to determine your needs.
|Room Size (square feet)||Btus/hr|
These guidelines are a general rule of thumb, and it’s important to note that air conditioners are rated for standard ceiling heights of eight feet. If you have higher ceilings, or if you’re trying to cool a warmer, south-facing room, look for an air conditioner with more power. Poor insulation or drafts will also affect air conditioner performance, so it’s a good idea to remedy these problems if you have the right size air conditioner and it’s working too hard.
Room air conditioners can either be mounted in a double-hung window or installed through an exterior wall in your home. Both methods are effective, but a well-insulated wall mount tends to perform a little better than a window air conditioner that uses stops to seal the gaps between the air conditioner and the sides of the window opening.
In general, wall-mounted air conditioners are a good choice for a room that needs to be cooled for more than half the year. Window air conditioners are best in places with cold winters, because you can remove them and let storm windows keep the cold out. Most air conditioners include side stops, which gives you the choice of using the air conditioner in a window or installing it through the wall.
Mounting an air conditioner through a wall requires the help of a builder. This is a structural change to your home that needs to be properly framed to ensure safety and prevent leaks. You may also have a choice between an air conditioner that plugs into a wall outlet and one that can be hard-wired into your home electrical system. If you live in a place where it snows, consider purchasing a fitted cover that will keep snow and ice out of the air conditioner’s compartment.
You can install a window air conditioner yourself. Measure the size of your windows and try to find an air conditioner that fits snugly, as you’ll get an efficiency boost by reducing the amount of space filled by the air conditioner’s side stops. Look for side stops made from flexible materials that won’t crack or break over time, and try to find side stops that offer some insulating value.
Be sure that your window sills are free of decay and strong enough to support the weight of an air conditioner. You’ll also need a three-prong electrical outlet near the window. Air conditioner cords tend to be on the short side, so keep this in mind when deciding which window to use.
The U.S. Department of Energy reports that replacing a 10-year-old air conditioner with a modern, more efficient model will save an average of $25 a year on your electric bill. That means less electricity consumption and a smaller carbon footprint for your home.
Look for an air conditioner that has earned the Energy Star. These air conditioners are 10% more efficient than comparable models. Also look for an air conditioner’s Energy Efficiency (EE) rating. This rating divides the Btus/hr by the wattage an air conditioner consumes. Higher EE ratings provide more cooling with less power.
We've compiled this group of information links to help you further your research: