Air Conditioning and Electricity Bills

Have you ever wondered what it costs to run an air conditioning unit or system at home or in the workplace and if you could get that cost down in any way?

There are some simple enough calculations you can do to help you decide how much your air conditioning is actually costing you.

People are often surprised when they see how much of their monthly electricity usage is taken up by their cooling system.

A Working Example

Let's take an example of the cost to operate a single room air conditioner for a day as well as for a month. Generally, the higher the BTU rating of the AC unit, the more electricity it will consume.

air conditioning and electricity billsRemember also that the energy consumption will vary by make and model.

An Average AC

The average air conditioner that is used in the U.S. is approx 3 tons and carries a 10 SEER efficiency rating. It may not surprise you to learn that a unit of this size will draw approx 2.9kW (kilowatts, or 1,000 watts) per hour.

To obtain the approximate cost per hour of runtime, simply multiply this number by the electricity cost per kilowatt hour.

Depending on your area, electricity costs can vary a great deal. The cost can also vary depending on the time of day.

As a hypothetical example, lets take that cost to be 0.18 cents per kilowatt hour baseline to say 0.45 cents per kilowatt hour peak time.

I'll use the baseline energy cost of 0.16 cents per kilowatt hour for my calculation.


2.9 x 0.18 = 0.522 cents per hour

This cost will be more than double during peak time electricity demand.

Let's now assume we'll have around 1,200 hours of cooling time in summer and in this example, the total cost to run a 3 ton 10 SEER air conditioner can range from $626 to over $1,200.

If your air conditioning unit is rated below 10 SEER or your local electricity costs are higher (as they doubtless will be) as per this example, your costs will be higher.

To give you some idea, an 8 SEER AC is 20% less efficient than a 10 SEER AC. This means your cooling costs will be around 20% higher.

What Are Kilowatt Hours?

To help you understand what a kilowatt-hour (kWh) is, it is basically the standard unit of measurement for electricity in most of the world.

What it means simply is using 1,000 watts of electricity for one hour.

If you want to calculate what your air conditioner's running cost is for an hour, you can usually find its wattage rating printed on the box or you can look it up online. Then simply multiply this by how many hours it is used each day.

As an example, a 2,000 watt rated air conditioner will consume 2 kWh (2,000 watts per hour).

To give you a comparison, a 10-watt LED light running for an hour will use 0.01 kWh (10 watts divided by 1,000).

The cost of electricity varies from state to state and from town to town. Simply check your own electric bill to see what it costs you.

Calculating Air Conditioning Electricity Costs

To calculate a window air conditioner's energy usage, you can divide the BTU rating by the SEER rating to give you the result in watts per hour (or watt hours).

Then divide the result by 1,000 to get kilowatt hours (kWh).

This is how the electric company calculates energy bills. Multiply the kWh by the power company's rate and you'll have the cost per hour.

Another Example:

Let's take a 14,000 BTU, 10 SEER rated air conditioner with a cost of 45 cents per kWh and calculate:

14,000 BTUs / SEER 10 = 1,400 W = 1.4 kWh

1.4 kWh x $0.45 = $0.63 per hour to run your air conditioner.

Multiply that by 8 hours per day for the 125 days of summer and your air conditioner has an annual running cost of $630 a year.

Cutting Costs

There are a number of ways to cut the cost of running an air conditioner.

Start with a programmable thermostat that you can program at a few degrees higher temperature during the day and at night while you sleep. One of the biggest mistakes people make that costs them a lot of money is to set the thermostat too low.

There's not much comfort to be had sitting in a freezing cold room at below 60°F when it could be much more comfortable at a balmy 75°F.

Shading the house from the sun where possible will reduce the amount of work the air conditioning will need to do to keep it cool inside, which will also save a lot of dollars.

Drawing the blinds and lowering awnings during the day while opening windows at night to catch the cooler breeze can also save you money.

When purchasing a new air conditioner, be sure to look for Energy Star units. These can use up to 14% less energy than government requirements. They may also entitle you to a tax credit if available in your state.