A Formula to Calculate the Electricity Cost of Household Electric Appliances

When a person operates any electric appliance in their home it gets measured at the electric meter. Those units of measurement are known as kilo-watt hours (kWh). Each electric utility company charges a different rate for each kilo-watt hour (kWh) used. Currently where I live the cost is .10631 or approximately 10.6 cents per kilo-watt hour (kWh).

The first thing a person needs to know is how many watts the appliance in question uses. That can usually be found on any appliance label or nameplate. Appliance labels will state the volts, amps and watts and some labels will state only the volts and amps, not the watts. If the watts are not listed just multiply the volts times the amps and the result will be the watts. Example: 120 volts X 10 amps = 1200 watts. Once a person knows the watts of an appliance they can easily figure out how many kWh's that particular appliance is using.

A kilo-watt hour (kWh) is 1000 (kilo) watts of energy being used in a one hour period. A 1000 watt appliance that is turned on for 1 hour equals 1 kilo-watt hour. That 1000 watt appliance would cost me 10.6 cents every hour it's in operation.

Here are some simple examples:

I have a 100 watt light bulb on my front porch that is turned on approximately 5 hours every evening. I am paying about $1.59 a month on my electric bill.

100w X 5 hrs = 500w divided by 1000 = .5 kWh every evening. Multiply by 30 days/month.
.5 kWh X 30 days = 15 kWh a month.
15 kWh X 10.6 cents (.106) = $1.59 a month on my bill. (About 5 cents every evening).

I have a 12 cup coffee maker that is on approximately 2 hours every morning. The label on the bottom of the coffee maker reads 7.5 amps, 120 volts. To find the watts you multiply amps X volts, 7.5a X 120v = 900 watts. I am paying about $5.72 a month on my electric bill.

900w X 2 hrs = 1800w divided by 1000 = 1.8 kWh every morning. Multiply by 30 days/month.
1.8 kWh X 30 days = 54 kWh a month.
54 kWh X 10.6 cents (.106) = $ 5.72 a month on my bill. (About 19 cents every morning).

We have a 3.5 quart slow cooker (crock pot) that we will use on average about 8 hours, 7 times a month to prepare dinner. The label on the bottom reads 120 volts, 190 watts. The amount of watts is already given, no need to figure it out. I am paying about $ 1.13 a month on my electric bill or .16 each meal we prepare. Certainly an economical way to prepare dinner.

190w X 8 hrs = 1520w divided by 1000 = 1.52 kWh each meal. Multiply by 7 meals/month.
1.52 kWh X 7 meals = 10.64 kWh a month.
10.64 kWh X 10.6 cents (.106) = $ 1.13 a month on my bill. (About 16 cents a meal).

A 10,000 BTU window air conditioner found on a popular electronic store website. This air conditioner will run from noon to 8:00 pm everyday. The label reads 8 amps, 115 volts. To find the watts you multiply amps X volts,
8a X 115v = 920 watts. To run this unit 8 hours a day for a month would be about $ 23.40 on your bill.

920w X 8 hrs = 7360w divided by 1000 = 7.36 kWh every day. Multiply by 30 days/month.
7.36 kWh X 30 days = 220.8 kWh a month.
220.8 kWh X 10.6 cents (.106) = $ 23.40 a month on your electric bill. (About 78 cents every 8 hour day.)

You can use this formula on every appliance in your home as long as you can find the appliance label. The most important things to remember is that amps X volts = watts, 1000 watts an hour is a kilo-watt hour (kWh) and that's how your billed by your local electric utility.

Dust, dirt, old filters, temperature, inoperable thermostats, weathered/cracked rubber seals, low coolant etc. all can effect the efficiency of electrical appliances.