How to calculate electricity cost by appliance

To get an accurate picture of your home's energy consumption, you’ll need 3 figures to calculate the electricity usage of each appliance or electronic device: 

• The wattage of the appliance
  
• The average number of hours you use it per day
  
• The price you pay per kilowatt-hour (kWh) of electricity

Your kWh rate is printed right on your electric bill, and you can estimate your average daily use. To determine the wattage of an appliance, look for a label or metal plate, which is usually in an inconspicuous place like the back or bottom of the appliance or device.

If the wattage is listed, it will have a “W” at the end. If you can’t find a label, check the appliance’s original documentation or try searching online for its technical specs.

Once you have your data, calculate the cost of use with this formula:

1. Multiply the device’s wattage by the number of hours the appliance is used per day
   
2. Divide by 1000
   
3. Multiply by your kWh rate

For example, if you have a 150-watt television that you watch 5 hours per day, it consumes 750 watt-hours per day (150 x 5 = 750). You'd then divide 750 by 1000 to convert 750 watt-hours into .75 kWh (750 ÷ 1000 = .75). If your electricity rate is 12¢ per kWh, that means it costs 9¢ per day to use your television (.75 x .12 = .09). That should account for about $2.70 of your monthly electric bill (.09 x 30 = 2.7).

It will take a lot of number crunching to do this with all the appliances, electronics, and lights in your home, so if you’re looking for an easier way, turn to technology.

Tech tools and kWh calculators to estimate your electricity bill

Even if you know how to calculate your electric bill with just a pen and paper, you can learn much more about your energy consumption with a technological upgrade.

Companies like Neurio, Curb and Sense have designed products that can connect to your home’s main electrical panel and recognize the unique electrical signatures of the appliances in your home. Each product works somewhat differently, but most allow you to view detailed breakdowns and analyses of energy usage using an app or web browser.

This kind of information comes at a price, however ⏤ you should expect to pay a few hundred dollars for a system like this, and some require an electrician to install it at an additional cost.

There are some less expensive tech options. One is to use smart plugs, which are outlet adapters that can be controlled from anywhere using a mobile app. Some smart plugs ⏤ but not all ⏤ feature wattage monitoring that you can use to verify the wattages of appliances throughout your home and track the energy consumption of the ones you use most often. 

An even less expensive tool is an electricity usage monitor with a built-in digital display, such as the Kill-A-Watt meter. It won’t give you a detailed analysis, but it will give you a quick read of the electrical draw of any appliance you plug into it, saving you time in your calculations. Some models can automatically calculate kWh totals by day, week, month or year.

Assess your home’s energy efficiency

Not sure what to do with all this new data on your home energy use? Take a minute to enter your zip code at Home Energy Saver, an online energy assessment tool from the U.S. Department of Energy. You can use this tool to see average energy use estimates in your area for typical and energy-efficient homes and generate customized energy efficiency recommendations for your home.