The most common room air conditioners are window units. Designed for double-hung windows, the kind that opens by sliding the bottom half up, window ACs are easy to install and easy to remove come fall.

Just slide the window open, rest the AC on the sill, close the window, and secure it in place. If the air conditioner isn't as wide as your window, most include side curtains to fill the gaps. While it's common to put window ACs in storage when the weather cools, they can also be installed permanently.

Window air conditioners pull in the hot air from your room and run it over a cooling coil before returning blowing it back into the room. Passing the hot air over the cooling coil also pulls moisture from the air, creating dew. The dew is funneled outside, as is the heat produced to keep the cooling coil cold.

Innovations in designs have greatly improved the energy efficiency of window air conditions in recent years. From high-efficiency compressors to energy-saver settings, these improvements help you save money while staying cool. Look for ENERGY STAR certified models to cut down on electricity costs. Even better, compare the Energy Efficiency Ratio (EER) or the Seasonal Energy Efficiency Ratio (SEER) of any models you're interested in. The higher the number, the more efficient the air conditioner.

The SEER details a model's average efficency over a range (65°F to 104°F) of outside temperatures. The EER bases its figure on a steady outside temperature of 95°F. If you primarily use your AC when outside temperatures are 95°F or higher, the EER will be a more accurate figure. Otherwise, look to the SEER. Don't worry if the model you're interested in only providers one or the other. Either number will still give you a general sense of the model's efficency.

A casement air conditioning unit is designed for windows that open horizontally or swing-out (usually with a hand crank) instead of vertically. Casement ACs are basically taller skinnier window units.

If you can't mount an AC to your windows, a portable air conditioner might be the best option. These models usually rest on the floor and use a flexible hose to vent hot air outside. The venting hose can usually fit through a small space, such as the center vent often found in basement glass-block windows.

While it can be convenient to roll your AC between rooms, portable air conditioners have their share of drawbacks. Most notably, they're less efficient and noisier than window units. While window models can project their noise outside, a portable air conditioner doesn't have that option. Similarly, portable ACs need to spend energy pushing excess heat outdoors while window units can let that heat passively radiate out.

Portable air conditioners also remove moisture from the air just like window units. But, unlike window units, they can't just drip the moisture outside. Most portable air conditioners collect the water in a tank that must be manually emptied from time to time. Self-evaporating models need to be emptied less often but aren't enitrely hands-off. Other models allow you to attach a drainage hose to manage the water it collects.

For a more permanent solution, consider a wall air conditioner. These models extend from a wall instead of a window and require a sleeve to be properly installed. Often more efficient than window models, through-wall air conditioners are a good way to stay cool without sacrificing one of your windows. However, installing an in-wall AC isn't as easy as installing a window unit. Unless you're comfortable cutting holes in your wall, hire a contractor. If you're in the Chicagoland area, we here at Abt would love to help!

Packaged Terminal Air Conditioners (PTACs) are in-wall units that can heat and cool your space. In-wall units are left in place year-round. Having one appliance to warm you up in the winter and cool you down in the summer just makes sense. If winter temperatures even approach freezing where you live, be sure to get a PTAC with electric heat. The alternative, heat pumps, are less expensive. But they're also less efficient.

If you're looking for a whole-home solution, Central Air Conditioning Systems are the way to go. Usually, one main unit pumps cool air through ducting to each room in the building. While these systems are more expensive than the other options, they are much more convenient. Upfront and energy costs are both higher with a Central Air Conditioner. Because instead of using room air conditioners to manage specific areas of your home, central air keeps your whole house cool.

Central air systems with zone controls combine the convenience or a whole house system with the localized controls of window and portable ACs. These systems include thermostats in each room so that you can precisely manage temperatures anywhere in your home. This versatility can be especially useful for poorly insulated or especially sunny rooms.

If you are looking to do away with portable or window air conditioners, Abt is licensed to install central air systems. This service is only for our Chicagoland customers. Give us a call at 800-860-3577 so we can find a time to come look at your home and provide an estimate.

Mini-split AC systems are electric heating and cooling systems that do not require ductwork. They consist of an indoor unit and an outdoor compressor. The indoor units install above a doorway or just below the ceiling. These highly energy-efficient devices are a great whole-home climate solution. By installing indoor units in every room, each member of your family can dial in their ideal temperature for maximum comfort. Depending on the model, one compressor can control up to eight rooms.