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A Guide to Understanding Air Conditioner Energy Consumption

A Guide to Understanding Air Conditioner Energy Consumption

September 19, 2022

AC Energy Consumption in Norcross, GA

Keeping your home cool and comfortable throughout the summer usually means paying high energy costs. An AC unit generally uses much more power than any of your other appliances and keeping it running all summer can be costly. That being said, exactly how much energy your AC uses will depend on how big it is, how efficient it is, and how hot and humid the weather is. With this in mind, here is a handy guide that tells you everything you need to know about air conditioner energy consumption.

How to Determine How Much Power Your AC Uses

Determining how much power your AC uses is contradictorily both simple and a little complex. The simple part is figuring out how much energy the unit uses for every hour it runs. The AC condenser outside your house should have a small panel that lists its specifications. This includes its size (measured in tons) and SEER rating.

You should also see the power consumption. This is measured in watts per hour and shows exactly how much electricity the unit will consume if it runs for a full hour. Unfortunately, this number on its own doesn’t really tell you much in terms of how much total energy the unit will use for a few different reasons.

For starters, the total energy consumption will be mostly determined by how many hours the AC unit runs. As we said, this is determined by the unit’s efficiency and the weather conditions. The insulation level of your home also plays an important role. Let’s now look at some of the other factors that can also affect AC energy consumption.

Understanding Surge Wattage

Let’s say that you have a 3-ton AC unit. In this case, it will likely be rated somewhere around 3,000 to 3,500 watts per hour or 3 to 3.5 kilowatts per hour (kWh). This is the amount of electricity the unit uses when running, but it does not include the additional energy needed to start the unit.

It takes a large surge of energy to start the AC unit, and this is known as surge wattage. On most AC units, the surge wattage will typically be at least several hundred watts more than the running wattage. This means that if your AC uses 3 kWh, it likely consumes around 3,800 watts per hour in the few seconds it takes for the compressor and fan motors to start.

It is important to note that this doesn’t mean your AC will use 6.8 kWh, as the increased surge wattage only lasts for a few seconds. The surge wattage only means that your AC will use more watts in the first hour it runs. If it continues to run continuously for additional hours, it will continue to use only 3 kWh.

Surge wattage is important to note because if your air conditioner turns on and off multiple times every hour, this will often use more energy than if it ran continuously for the entire hour. This problem can be especially pronounced if your AC system has any issues that cause the unit to short-cycle, which is when it turns on and off constantly without completing a full cooling cycle. When this happens, the AC is basically stuck in start-up mode, meaning it is constantly drawing the surge wattage.

The easiest way to avoid this problem is to make sure to have a certified AC technician maintain your cooling system every spring, which is something we can help with. You should also immediately contact us if you notice any issues with your AC system; we should be able to repair the problem before it turns into something more serious.

How SEER Rating Impacts Energy Usage

SEER stands for seasonal energy efficiency ratio and is the system used to measure the energy efficiency of central air conditioners and other cooling units. SEER is calculated by dividing the total BTUs the unit produces by the number of watt-hours it consumes.

Just because two AC units both are rated at 3,000 watts per hour does not mean that they will consume the same amount of total energy. Again, the total energy consumption is dictated by the number of hours the unit runs, and, obviously, the more efficient the unit is the fewer total hours it will run.

This is why SEER is important as it gives you a better idea of approximately how much energy the unit will use throughout the entire summer. In this way, you can compare different models in terms of purchase price and energy consumption to find the best one.

Single-Speed vs. Variable-Speed AC

Another factor that determines total energy consumption is whether your AC is single-speed or variable-speed. Lower-rated AC units are usually single-speed, which means that the compressor and fan motors always run at full strength. Variable-speed ACs can slow down the speed of these motors, which allows the unit to use much less energy. This happens any time when less cooling is required, such as in the morning, at night, on milder days, or even when the temperature is only a degree or two above your thermostat setting.

During these times, power consumption can decrease by 75% or more. Since the speed slows down, the unit will take longer to achieve the set temperature than it would if it ran at full speed. While this may sound like a bad thing, it really isn’t since it will only happen when the home is mostly already cooled. In fact, running at a lower speed for a longer time provides some important benefits in addition to using much less energy.

One reason is that it eliminates the issues with higher energy use from surge wattage caused by the unit turning on and off every 15 to 20 minutes. Many single-speed ACs will run for this long and then turn back on again after five minutes or so. This will obviously use far more energy than if the unit ran at only partial power for the entire hour.

Another major benefit of running for a longer time is that it allows your AC system to manage your indoor humidity level more effectively. The longer the system runs, the more moisture it can draw out of the air. This, in turn, further improves the efficiency of your AC system. This is because the more moisture there is, the hotter the air is, so it takes much more energy to cool extremely humid air than it does to cool the same volume of dry air.

How Much Power Does the Blower Fan Use?

The final piece of the energy consumption puzzle is the blower fan. This is important because the watt-hours listed on your AC unit do not include the energy used to power the fan inside your house. Most residential blower fans use around 500 watts per hour. If you have a much larger house, it could be slightly more than this. If that same 3-kWh AC unit ran for an entire hour, your cooling system would use 3,500 watts in total. However, if you leave the fan set to “Auto,” which is always recommended, the fan will only run when the AC condenser is also on.

If you have any questions about SEER ratings or AC energy consumption, the experts at Bardi Heating, Cooling & Plumbing are happy to help. We specialize in a full range of AC and heating services for residents of Norcross and the Greater Atlanta area. Our technicians can maintain your cooling system to ensure it is working at peak efficiency. If you’re looking to upgrade or replace your old AC unit, we carry a range of high-efficiency models and can handle the installation from start to finish. We also offer plumbing and indoor air quality services. For more information, or if you need any HVAC services, give us a call today.