If you have to replace a system the first thing most people think is, “give me the same thing I had.” In most cases whatever size you had before will work for the replacement system, but there are circumstances where it will not. For example, if you added windows or doors, added new rooms, zoned off unused rooms, or added insulation you may have affected the amount of cooling that is required. Some people want to install a larger system “just to be safe,” but in reality this can cause problems down the road. If your system is too big for your space your electric bill will be higher and you could negatively affect the system’s ability to control humidity, which can lead to several other problems. When it comes to replacing a system, if you’ve made any of the changes above it’s worth having a contractor perform a load analysis of your home to properly size the unit for your needs. If you don’t feel comfortable with the way your contractor is analyzing your space, call another and get a second opinion. They should walk through the home and ask you about comfort and usage, not just ask about square footage.