When it’s sweltering hot outside, there’s nothing like a nice cool, refreshing air conditioner waiting for you inside the house. While some places have central air or a swamp cooler that isn’t always practical, affordable, or efficient. Enter the wonderful invention known as the window air conditioner. The AC units are ineffective, out-of-the-way means of attaining cool air while getting the most out of their design and power. If you’re on the fence about getting one of these units for your own home this summer, take a look at our list below to help you decide if a window air-conditioner is right for you.

How Well Does It Cool Your Space?

Window air conditioners typically run between 5,000 – 20,000 British Thermal Units (BTU). One square foot of space requires approximately 20 BTU per square foot to effectively cool the space. Therefore, the best way to find out if an AC unit will cool your space well is to measure the size of the room and get the appropriate size AC unit. With that in mind, a good rule of thumb is that smaller rooms will only need about 5,000 – 7,000 BTU and it’ll only increase as the room’s size increases. You’ll need to make some adjustments based on variables within the room as well. For instance, if the room has a lot of shade, you’ll need to reduce that capacity by at least 10%. Conversely, a sunny room would require an increase of the same amount. The number of occupants in the room at any given time can also affect an AC unit’s efficiency, so be sure to add around 600 or so BTU for each additional person that may occupy the room. If you have a family of four and all of them will occupy the room at one point or another, you’re going to need to get an AC that’s at least 1800 BTU higher than the one you’d normally buy for the room.

Is It Energy-Efficient?

Running an air conditioner all summer can get pretty expensive, depending on a number of factors. Ask yourself the following questions to determine how efficient your air conditioner will be: How often is it running? What’s its efficiency rating? You can get an idea based on researching specifications or—if you’re mathematically inclined—can calculate it yourself. To help with making your AC more energy-efficient, consider getting a model that has a built-in energy saver function. Energy savers are always a wise investment. Energy savers reduce power consumption by automatically turning off the circulation and exhaust fans whenever it detects the compressor has been switched off. While the AC unit is in operation, the system automatically cycles both fans on/off while the compressor is running. This effectively keeps things cool while reducing the environmental impact and power consumption of the unit. Other methods can include a thermometer to gauge the temperature or a timer that allows you to set up specific parameters for how often it should be running, a shut-off threshold, and a temperature setting.

Consider How It Will Be Installed

When you’re performing home improvement tasks or replacing appliances, obtaining the proper measurements will save you a lot of trouble in the long run. Additionally, knowing where you’re going to place an appliance and what kind of unit you’re planning to get is just as essential. There are three types of AC units to consider here: portable, wall-mounted, and window AC units. Portable AC units are great for limited use, very small spaces, and some portability. However, they don’t have great efficiency and are really only a step above an oscillating fan. Wall units are great for centralized cooling but tend to require a lot of maintenance over time.

A better bet may be a window air conditioner, largely due to its low cost, sleek energy-efficient design, and ability to be placed in an out-of-the-way location and still be useful. In the end, it really just depends on your home’s layout, design, and cooling needs.

Power Requirements

Power is essential to a fully functioning AC unit. You need to make sure the AC doesn’t require more power than your room can handle and that it’s operating efficiently. Figuring out the power needs of a particular unit comes down to how much wattage it’ll use relative to its output and efficiency. There’s no serious math required here. Keep in mind smaller units (around 5,000 BTU) should only use around 450 watts. Mid-size units (8,000 BTU) require around 715 watts and larger ones (14,000 BTU) should use around 1,250 watts. Window AC units will always be more efficient and use half the electricity required for a portable unit.

Maintenance and Repairs

The last part of buying a new AC unit is perhaps the most important—planning for repairs and maintenance throughout the life of the unit. A window AC with a case on it automatically moves moisture outside, so there’s no need to worry about emptying it. But that doesn’t mean you shouldn’t come up with a maintenance plan. AC repairs can get pretty pricey, costing an average of $224 at a time It could go even higher than that. If you hear rattling, strange humming, or spot other signs of a mechanical issue with your AC unit, it’s wise to look into doing some repairs. But the best way to prevent issues in the first place is to plan for some periodic maintenance. Replace your filters, clean them if they’re washable, and spend some time acquainting yourself with how your AC unit works so you can keep everything in clean, working condition.