How to Calculate Your Home's Monthly Energy Usage

We’d all love to see our energy bills shrink, but it’s not always clear which appliances and devices contribute the most to monthly energy costs. Electricity use shows up on the bill as one lump sum, and if we could see an appliance-by-appliance breakdown of energy consumption, we could develop more effective energy conservation habits.

Technology to make that possible is on the horizon, but we’ll get back to that later. First, we’ll show you how to calculate your energy consumption the old-fashioned way.

Calculate Your Appliances’ and Electronics’ Monthly Usage

You can calculate a decent estimate of how much an appliance or electronic costs to operate each month if you know the wattage, the average amount of time you use it each day, and your current electricity rate.

Most appliances and electronics have a small label that lists the wattage along with other information. Sometimes this information is stamped into metal, like on the base of a light bulb. If you can’t find the wattage on the device itself, you may find it in the user’s manual or on the manufacturer’s website.

To calculate the energy consumption cost, start by multiplying the wattage of the device by the average number of hours you use it each day. This gives you the watt-hours per day. So, if you have a 120-watt television that you use four hours per day:

120 x 4 = 480 watt-hours per day

Next, divide the watt-hours per day by 1,000 to convert it into kilowatt hours per day, or kWh per day:

480 / 1,000 = .48 kWh per day

Since we’re calculating the energy consumption over a month, you’ll want to multiply the kWh per day by 30

.48 x 30 = 14.4 kWh per month

Finally, multiply the kWh per month by your electric provider’s kWh rate, which you can find on your monthly energy bill. This will give you an estimate of what the device costs to operate per month. So, if you pay 12 cents per kWh:

14.4 x .12 = $1.73 per month

It costs only $1.73 to run this television as usual for a whole month. Repeating this process with frequently used appliances and electronics throughout your home will help you see a clearer picture of where your electricity dollars go.

Check the Energy Label

If you don’t feel like crunching so many numbers, you can also get an idea of how much it costs to operate an appliance by checking its Energy Guide label.

These distinctive, black-and-yellow labels can be found on most appliances at the point of purchase, as required by the federal government. They break down these same calculations using the national average kWh rate and a standardized measurement of average use.

This provides an easy shorthand for comparing the energy efficiency of appliances in an apples-to-apples way, but it won’t provide results as accurate as your own calculations, which are based on your exact kWh rate and your own usage estimates.

Automate the Process

If all this seems like a lot of work, there are tech developers who agree. Tech startups are making big investments in “energy disaggregation” technologies that aim to perform these calculations for you, accurately, and in real time.

While this is an emerging technological field, the industry hopes to create devices that can make automatic energy efficiency recommendations and can even sense when an appliance or device is malfunctioning.

So, while it doesn’t hurt to be able to calculate energy consumption on your own, the future promises ever-easier solutions for saving energy and money.


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