Air Conditioner Running Cost Calculator

Cooling capacity (BTU per hour)

BTU per hour measures how much cooling the unit delivers. One "ton" of cooling is 12,000 BTU per hour.

1. Window or portable unit: look for a sticker on the side, back or inside the front panel, or the box or manual. It is listed as "cooling capacity" or "BTU/h". The size is also often in the model name, such as "12000".
2. Central air conditioner: find the data plate, a metal sticker on the outdoor unit. It lists the model number. The model number usually contains a number such as 24, 30, 36, 48 or 60, which is the capacity in thousands of BTU: 24 is 2 tons (24,000 BTU), 36 is 3 tons, and so on. Brands differ, so check the manual or search the model number to confirm.
3. Ductless mini-split: the label on the indoor unit or the manual lists capacity, often 9,000, 12,000, 18,000 or 24,000 BTU.
4. Cannot find it? Search the brand and model number with "specifications", or ask the installer or the company that services the unit.

Use the unit you actually have. Do not guess from the size of the room.

Efficiency rating (EER or SEER)

EER and SEER show how much cooling you get per unit of electricity. A higher number means a lower electric bill.

1. Window or portable unit: look at the yellow EnergyGuide label, the box or the data plate. It lists EER or CEER.
2. Central air conditioner or heat pump: the data plate or manual lists SEER (newer ones list SEER2). The free AHRI directory (opens in a new tab) will find it from the model number.
3. Newer ratings, such as SEER2, EER2 and CEER, come from stricter tests and are numerically a bit lower. Just enter the number on your label. The tool treats it as an estimate.

Cannot find it? As a rough guess, try about 10 for an older unit and 14 or more for a recent high-efficiency one.

Running hours per day

The hours the cooling compressor actually runs, which is less than the hours the home is occupied.

1. Smart thermostats such as Nest and ecobee, and many app-connected ones, report daily "run time" for cooling. Use a typical hot-weather day.
2. For a window unit, a smart plug that tracks energy shows how much it uses. Divide the kWh by its power draw in kilowatts to get the hours.
3. No data? Try 6 to 8 hours for a typical summer day, and 10 to 14 for very hot days, and compare the results.

Days in the cooling season

How many days a year you run the air conditioner.

1. Count the months you use it. June to August is about 90 days. Mild climates may be 30 to 60, and hot ones 150 or more.
2. Your electric bills show the months with higher use.

Electricity rate ($ per kWh)

This is what your utility charges for each kilowatt-hour (kWh) of electricity.

1. Open your latest electric bill (paper, email, or your utility's website or app).
2. Look for a line called "price per kWh", "energy charge" or "rate". It is often shown in cents, so divide by 100 (17 cents is 0.17).
3. If the bill only shows totals, divide the total electricity charges by the kWh used. This quick all-in rate includes fixed fees, so it runs a little high.
4. If your rate changes by time of day or by how much you use, use an average, or the rate that applies when you use the appliance most.

No bill handy? About 17 cents is a rough US average, so the pre-filled value is a fair start. Rates vary a lot by state and utility, so your own number is better.

See the average residential rate for every state