Central air conditioning equipment can last for well over a decade, but the time eventually comes to replace your old system. Installers often recommend replacing all parts of a system together, which makes this a great time to upgrade. Installing a newer, more efficient air conditioner can mean better cooling while also offsetting some of the cost with reduced utility bills.

Of course, it can be helpful to know just how much money you'll save. Unfortunately, the measurements used on many air conditioners may seem like a foreign language if you aren't familiar with them. Just what's a BTU or a SEER rating, and how can you use these values to estimate your energy usage? Fortunately, it's not too hard to understand how these pieces of the puzzle fit together.

British Thermal Units

It doesn't matter whether you're looking at a new central air conditioning system or a humble window unit, they all measure capacity in the same way: British Thermal Units (BTUs). If you look up the strict definition of a BTU, you may be left wondering what heating water has to do with air conditioning. Luckily, the details aren't essential to understanding the efficiency of your new air conditioner.

Instead, there are two critical facts to remember: a higher BTU air conditioner will cool a larger space, and the BTU rating of your unit is per hour. Recognizing that BTUs represent energy over time will allow you to see how they can help you to estimate your air conditioner's utility cost.

Seasonal Energy Efficiency Ratings

Next up is the Seasonal Energy Efficiency Ratio (SEER) rating. All central air conditioning systems use SEER to provide an at-a-glance comparison for energy efficiency. This number tells you how many BTUs your new air conditioner can provide per watt-hours of energy consumed. In other words, a higher SEER number means more cooling for less energy usage.

Putting It All Together

These two units together allow you to estimate the hourly running costs for your new air conditioner. By dividing your air conditioner's BTU capacity by its SEER rating, you'll get the total energy consumption of the unit in watts per hour. Since most energy companies bill by the kilowatt-hour, you'll need to divide this value by 1000 to get a number that you can use with your electricity billing rate.

Most people don't worry about their energy consumption on an hourly basis, however. If you want a more useful figure, then estimate the total number of hours that your air conditioner runs per month. You can then use your monthly usage in hours along with your air conditioner's hourly energy consumption to come up with a ballpark estimate of your new air conditioner's monthly operating cost.