When you're ready to invest in an air conditioning unit for your home, you want to think about your budget but also ensure you invest in a model that will be strong enough to actually keep your home cool and comfortable. On the other hand, an oversized unit that offers too much power can mean a waste of money. Note a few tips for choosing the right type or model of air conditioner for your home.

Calculating power

The cooling power of an air conditioner is measured in BTUs, or British Thermal Units. The BTUs will tell you how much space an air conditioner can cool, not the size of the air conditioner itself. Older window models may be very large but very inefficient and offer lower BTUs, whereas an updated window unit may be smaller but more efficient and able to cool a larger area.

Before you buy any air conditioner, note the size of your home or the room in which you want it installed and the recommended BTUs for that space. You'll then also want to increase the BTUs for very hot areas like kitchens, sunrooms, or any space that gets full sun or is not well insulated. As an example, a window air conditioner for about 18 square meters or a 3x6 room may require an 8000 BTU unit, but if the room is a kitchen or it's in full sun, you might increase those BTUs by 10%. 

Do the same if the space is very shady or relatively cool. Decrease the BTUs by 10% if there is a large shade tree over the space or if it's usually only occupied by someone who may actually enjoy a warmer temperature indoors. 

Selecting window models

If you live in a moderate climate and notice that you only need to cool one room on occasion, such as just the bedroom or a small living room during midday, a window unit can actually be the best choice. You don't need to cool your entire house when only one room is occupied or is the only room that needs cooling. When choosing a window unit, be sure it's lightweight enough for you to manage on your own and won't require bracing outside if it will be in a second-story window, as installing a shelf or support board can be a difficult job at an elevated height. 

Measure the window carefully and opt for the right model for a double-hung versus single-hung window. Window models will also have a recommended BTU measurement, and this too should be increased or decreased according to sun exposure or other such conditions.