Published: May 17, 2022
With California experiencing hot weather throughout the year, keeping your home cool can be quite costly. Still, the actual costs can vary depending on how efficient your air conditioner is and its size. With this in mind, here is everything you need to know to determine how many watts your air conditioner uses and estimate your average yearly costs.
Standard AC Sizes and Wattages
Central air conditioners are measured in tons, and residential central AC units usually range from 1.5 to 5 tons. Once you know the tonnage of your AC unit, it is easy to determine how many watts it uses per hour. This is because 1 ton of cooling capacity equals 1,000 watts of electricity usage. That means that a 1.5-ton AC would use 1,500 watts per hour, and a 5-ton unit would use 5,000.
If you want to estimate energy usage, it is easiest to convert from watts per hour to kilowatts per hour (kWh). This is because electricity providers charge by kilowatt-hour. To convert between the two, you need to divide the watts per hour by 1,000 since 1,000 watts equals one kilowatt.
Determining Actual Energy Usage
Knowing how many kilowatts per hour your AC uses is good, but it doesn’t tell you anything about how much energy the system will use each hour. This is because the system only uses power when the condenser and the fan are running. How frequently the unit needs to run depends on how efficient it is, how hot and humid the weather is outside, and the temperature inside the building.
The condenser will perform two or three cycles per hour, with each cycle lasting for around 15 to 20 minutes. Let’s say that you have a 2-ton AC that runs twice an hour for 15 minutes each time. In this situation, the condenser itself will consume 1,000 watts per hour (1kWh). Nonetheless, this doesn’t account for the additional energy used by the fan.
If your fan is turned to the “Auto” setting, it will also only run whenever the condenser is running. The average residential HVAC fan will usually consume around 750 watts per hour if it is left turned on all the time. This means that the fan will generally consume anywhere from 375 to 750 watts each hour, depending on whether you have it set to “Auto” or “On.”
Understanding SEER Ratings and How They Relate to Energy Efficiency
The energy efficiency of a central AC unit can vary quite a bit depending on how hot and how humid the weather is outside. This makes it almost impossible to accurately gauge the unit’s energy efficiency since it will fluctuate from day to day and even hour to hour. Researchers came up with the SEER (Seasonal Energy Efficiency Ratio) rating system to overcome this. This is the system used to measure the energy efficiency of all central ACs, heat pumps, and ductless AC units. Instead of simply taking a snapshot of the efficiency, SEER measures how much energy the system uses during one cooling season compared to how many BTUs (British thermal units) of cooling it produces.
To calculate SEER ratings, researchers test the air conditioner in various temperatures and humidity levels to simulate the average conditions throughout the summer. Each unit is measured to see how much energy it uses in temperatures ranging from 60 to 100 degrees and varying humidity levels. Following these tests, the researchers divide the unit’s cooling output by the total amount of energy consumed throughout the entire cooling season.
It is essential to understand that SEER is simply an average of how much energy the system will use per hour throughout the summer. Some people find it helpful to think about SEER in the same way you would the fuel efficiency of your vehicle. Even though your car is rated to get 25 miles to the gallon, that doesn’t mean it always will, as this is based on an average of its maximum efficiency. The same is also true for the energy efficiency of your air conditioner.
Using SEER to Compare Energy Efficiency of Different ACs
The main purpose of SEER ratings is to allow you to compare estimated energy usage or savings for different AC models. You can easily determine whether your estimated energy savings from a higher SEER unit are worth the additional purchase cost.
The federal government mandates that all new cooling equipment meet a minimum SEER requirement. Before 2006, the minimum standard in the entire United States was only 10 SEER. Currently, the minimum for California and all southern states is 14 SEER, whereas the minimum in the northern part of the country is 13 SEER. From January 1, 2023, the minimum requirements will rise to 15 SEER and 14 SEER, respectively.
Compared to using an old 10-SEER AC, upgrading even to a standard 14-SEER unit should reduce your yearly cooling costs by around 30%. On the other hand, a 20-SEER unit should consume 50% less energy than a 10-SEER AC.
You can find numerous charts and tools online from the U.S. Department of Energy that allow you to quickly calculate both total energy costs and approximate energy savings for units with different SEER ratings. These tools are convenient, but it is crucial to base everything on the total energy savings over the entire expected life of the unit instead of just looking at one year. You can easily compare the different purchase prices of the higher-rated unit to your estimated savings and determine whether the higher SEER unit is worth the added cost.
A central air conditioner will last for around 15 to 20 years. With this in mind, let’s say you want to see how much you can save by upgrading to an 18-SEER unit instead of the basic 14-SEER model. Using the average California electricity rate of 21¢ per kilowatt-hour, the 18-SEER unit should reduce your yearly cooling costs by 22%, or around $80 per year. This means that you could potentially save as much as $1,200 in energy costs over the unit’s life by opting for the 18-SEER model. If the price difference between the two units is lower than this number, the more efficient unit is the better choice.
Professional Air Conditioning Installation and Services
If you’re looking to upgrade or replace your old AC, the technicians at Tarpy Plumbing, Heating & Air can help you compare different units and determine what SEER rating is best. We are a Trane authorized dealer and a Mitsubishi Diamond Elite Dealer, and we carry AC and heating equipment suitable for buildings both large and small. Our expert HVAC technicians can also repair and maintain your home’s heating and cooling systems. We also have licensed plumbers on hand for drain cleaning, leak detection, pipe repairs, and a wide range of other plumbing services. Our company is located in Santee, and we serve the entire Greater San Diego area. Give us a call today for more information or if you have any questions.
Categories:HVAC
