How to analyze your electricity usage

How to analyze  your electricity usage

Q: I see gadgets being sold at home improvement stores that measure energy use for things plugged in at home. Would purchasing one help me save energy?

The gadget you mention is a watt meter. It's a device that measures the amount of wattage a plug-in electrical appliance uses. Some can monitor usage over a period of time. Most of them allow you to input your electric rate to determine how much it costs to run your television or toaster for a period of time. Some popular products include the Kill A Watt, Belkin Conserve Insight and Watts Up?. A watt meter may help you save energy if you change your habits based on what you learn from it.

You can do the same analysis with a pen and paper instead of purchasing a gadget. Here's how:

Determine the wattage. Most small appliances have wattage indicated on them, like a hair dryer, computer or coffee maker. It can be difficult to find the wattage on large appliances because it may involve moving the dishwasher, clothes washer or refrigerator, which is not very practical. If you can easily reach the plug, a watt meter would come in handy. The other option is to visit and click "Estimating Appliance and Home Electronic Energy Use" to see a detailed list of approximate wattage used by most home appliances.

Know your habits. How many hours each day is the television used? How long do you leave the coffee maker running each morning? How long do you use an electric space heater to warm up a room when it is cold outside?

Determine your electric rate. You're looking for the kilowatt-hour (kwh) rate. It should be between 10 and 16 cents for most households in North Carolina. You can find your kwh rate on your bill or by calling your electric cooperative. Another option is to do the math by dividing the dollar amount charged for a month of usage by the total kwh used in that month. Make sure that you are looking at the amount charged for the kwh (not fees, taxes, water or trash removal).

Do the math to determine the kwh usage and cost. I have broken it into two steps to keep it simple.

Step 1: (Device wattage x hours used per month) ÷ 1,000 = Monthly kilowatt-hour (kwh) consumption

(Monthly kwh consumption) x (kwh rate) = Monthly cost

Hair dryer example: My hair dryer uses 1,600 watts. I use it for 5 minutes every morning. That means I use it for 150 minutes every month (5 minutes x 30 days), which converts to 2.5 hours each month (150 minutes ÷ 60 minutes). My electric rate is $0.12 per kwh. I'm ready to use the formula.

Step 2: (1,600 watts x 2.5 hours) ÷ 1,000 = 4 kwh per month. Then, 4 kwh x $0.12 = $0.48.

Whew! It only costs $5.76 to use my hair dryer 5 minutes a day for an entire year ($0.48 x 12 months).

Television example: On the other hand, leaving your television on all the time costs a little bit more. My television uses 135 watts. Let's see what it costs per day.

(135 watts x 24 hours) ÷ 1000 = 3.24 kwh per day. Then, 3.24 kwh x $0.12 = $0.39 per day.

To leave it on all day, every day would cost me $142.35 each year!

Another good use of these plug-in watt meters is the ability to see how much energy an appliance uses when it is turned "off." Yes, many appliances use energy while waiting to be turned on such as DVD players, TVs, stereo systems, etc. and it can contribute to your overall power bill. We call that "phantom" or "vampire" loads — consuming energy while seemingly turned off. If you find "phantom watts" being wasted, a plug-in power strip with an on/off switch will stop the wasteful watts from flowing.

Your electric use can go down if you change your habits from what you learn. Suggestions to start include turning off electronics (power strip) while you are not using them, using Energy Star-labeled lighting products, replacing older inefficient appliances with Energy Star-labeled ones or simply hanging your clothes outside to dry. Involve everyone in your household, especially kids, and make changes to your habits at a speed that suits your family. The secret to success is making it a fun learning experience and a family team effort.

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Comments (1)

  • Sheila


    22 November 2014 at 06:01

    Thank you.Excellent information I needed to know.


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