How to Calculate Your Electric Bill

To calculate your electric bill, you’ll need to figure the energy usage of each of the appliances and electronic devices in your home. In an ideal world, estimating your electricity usage would be as easy as looking at an itemized grocery receipt. You’d be able to see exactly what you spent to run the dishwasher, do the laundry, watch TV and use a month’s worth of hot water. That technology is getting closer every day, but if you want to get an appliance-by-appliance breakdown right now, you’ll need to do a little math or spend a little money.

Calculate Energy Cost by Appliance

To get a truly accurate accounting of the energy consumption of your home, you’ll need to use some modern technology. But you may be able to calculate some decent estimates using some simple, old fashioned arithmetic.

To estimate electricity usage of a particular appliance or electronic device, you’ll need three figures: the wattage of the appliance, the average number of hours you use it per day, and the price you pay per kilowatt-hour (kWh) of electricity.

Your kWh rate is printed right on your electric bill, and the average daily use is easy enough to figure. 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:

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

So if you have a 150 watt television that you watch five hours per day, it consumes 750 watt-hours per day (150 x 5 = 750). Divide 750 by 1000 to convert 750 watt-hours into .75 kWh (750 ÷ 1000 = .75). If your electricity rate is 12 cents per kWh, that means it costs 9 cents 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 to Calculate Your Electric Bill

Even if you know how to calculate your electric bill with just a pen and paper, you can learn a whole lot 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 analysis 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 cheaper ways to involve technology in this process. 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 your most frequently used devices.

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, as well as generate customized energy efficiency recommendations for your home.