An air conditioner helps you maintain a comfortable temperature in your home. But, how do you know what size unit to buy? And, how long can you expect your team to last before it needs replacing? Read more to find out.

Measure your home before buying an air conditioner. You will need to know the size of your home. Measuring is easy, and there are a variety of affordable tools to help you do this. You can get a free estimate from an air conditioning contractor or use the free online Room Calculator on the Department of Energy website. Don't forget to measure window areas and ensure they're included in the calculation; windows generate heat too, so they have to be accounted for. You can also use indoor temperature logs – available online – to monitor temperatures in different rooms and compare them with normal temperatures.

Know your climate because your climate and location will also determine the system you need. For example, suppose you live in an area where your outside temperature usually stays over 90 degrees Fahrenheit. In that case, you'll need a unit that can cool an ample space to 60 degrees F – the desired inside temperature. There are energy-efficient units available for regions with warmer climates, so look for one of those.

Insulation and windows matter. If you have well-sealed and insulated windows and doors, it may be possible to lower your cooling load. Consider triple-glazed windows or high-performance insulation if you live in a warmer area. Another good option is having the exterior of the air conditioner unit facing towards the inside of your home – ideally, directly into the window. This will help keep cool air in a while, keeping hot air out so you don't overheat your home. However, there are issues with this as they can create challenging noise levels and may not be suitable for huge houses, where a big unit could make a lot of noise.

Have your air conditioner professionally installed. Installing an air conditioner requires expertise and best practices to prevent damage to the air conditioner and surrounding walls. You must avoid having sharp objects close to the unit and ensure you're using the correct size hose. If you can hear any leaks, then call a professional to get your leak fixed.

Check that your AC is professionally serviced. Professional service is necessary to ensure you get the best out of your air conditioner. It's better to fix a problem immediately – if not, chances are you'll still have the problem later and it could be a worse issue then. And if a serious issue arises, you might need the expertise of a technician.

A general rule of thumb is to replace your AC unit when it's 15 years old. But, you may choose to replace it sooner, depending on the local climate and the quality of maintenance you do. For example, if you live in an area with a hot environment and you're replacing your unit every 8-10 years, consider getting a more energy-efficient one to reduce your energy costs. And if you use coolant that doesn't contain CFCs or HCFCs and have maintenance done regularly, at least once every spring and fall, then the unit's life expectancy is much longer than 15 years.