How to Measure Home Power Usage (2022)

The modern home uses a lot of juice. Decades ago, it was simply appliances, lights, the radio, and the TV that consumed electricity. Today, it's all that and so much more: PCs, charging phones, always-on routers, DVRs, pool filters, security systems and cameras, baby monitors, smart speakers likeAmazon Echo—to name just a few.

There may not be much you can do about the draw from each item you've got plugged in at home. But you can at least contemplate saving if you measure exactly how much electricity you're using. It's possible to do so for each device—it takes some work to find all the so-called "vampire energy" (aka "vampire load" or "phantom load" or even "leaking electricity") that's being sucked away by devices in a standby mode.

That's right, even when you think something is turned off, it could still be using power—and in some cases definitely is, if the device is in standby or doing updates or talking to the internet. Finding those can be worth it. Americans were spending $19 billion per year on vampire energy as of 2015, according to an NRDC report(Opens in a new window), and we can safely assume things didn't get better. But how do you even try to put a stake in the heart of vampire energy?

Terms to Know (AKA the Boring Measurement Stuff)

When you're looking at your electricity bill, you're bombarded with a lot terms and abbreviations that seem pretty meaningless. Worse, they'll vary from country to country, because the United States can't ever agree to a standard used by most other locations. For this story, I'll talk mainly about the terms used in the US—specifically theKilowatt Hour.

The Kilowatt Hour (kWh, sometimes styled as "kW h" or "kW-h", but NEVER "kW/h") measures energy. It is about how much fuel is in something or how much energy is used over a certain time period. It's like a calorie or joule—they're all different ways to measure energy. For example, 172 Calories (technically kilocalories) is about 0.2 kWh. It's how we know the food we eat gives us energy, just as electrical power gives lights energy. It's possible that burning up food could power a light (if done exactly right)—that's why there are a lot of ways to measure energy.

While kWh implies a time period of energy usage, technically, it's not. It's actually the "equivalent to one kilowatt (1 kW) of power sustained for one hour," according to Wikipedia. Yeah, whatever.

The Kilowatt (kW) itself measurespower. It looks at how fast something is being used up. The more Kilowatts used, the more energy "burned." A kilowatt is 1,000 watts; one watt is the same as one Joule per second (J/s). Which is confusing, since J/s mentions a time frame (second) but it doesn't compare to kWh (which mentions hours, but isn't about time). Isn't science great?

What you really need to know: if a device is rated to use 1 kW of power, and if it operates for one hour at that level, it sustains 1kWh of energy. A device using 100 watts over 10 hours would utilize 1 kWh of energy (because 100x10=1,000=1kW). The Wikipedia example: a 40-watt bulb, used for 25 hours (40x25=1,000 watts = 1 kW) would also use 1 kWh (even though it took 25 hours to get there).

The kWh is how most home energy costs are calculated. You typically get charged a set few cents per kWh. So if the fee is $0.25 per kWh, that 40-watt (0.04 kW) bulb used for 25 hours (1 kWh) costs you a quarter. Right?

(Video) How to easily measure power consumption (& cost) of an electronic device

If only it was that simple.

How to Measure Home Power Usage (1)

My own bill from the central New York utility NYSEG lists, under Delivery charges, a basic flat service fee, then a number of fees that went toward paying the 786 kWh listed for me from Feb. 12 to March 9. That included a delivery charge, a transition charge ("the cost of making the electricity...industry more competitive"), revenue decoupling mech ("difference between forecast and actual deliver service revenues"), reliability support services charge ("cost incurred...for third-party services to ensure local electrical reliability needs are met"), and a New York state assessment required by law since 2009. Then there's something called SBC/RPS charges, used to fund clean energy efficiency programs, which differ from February to March.

Those are just delivery fees. There are more charges for the actual electricity supply, then taxes and surcharges from the county as well. The total for me to use 786 kWh: $84.07. These are typically lean months for my admittedly high electrical use household, since our heat is natural gas-based. Electricity use here spikes in July and August; that's air conditioner season.

Anyway, that's an expensive way of proving that it would be nice to know what to unplug and turn off more often to get the utility cost price down.

Measuring household kWh use is as simple as comparing bills every month, but that won't help you isolate devices that make slow-yet-lengthy draws on the supply from the local electric utility.

You can make a pretty good guess using theEnergy Vampire Calculator(Opens in a new window)from Duke Energy; put in a guess on how may PCs, chargers, TVs, monitors, printers, etc. you have plugged in full time, and it'll spit out a guess of how much you're wasting. Even that charger block or your smartphone is probably costing you something with no phone attached.

How to Measure Home Power Usage (2)

To get specifics regarding your energy usage, you only need one tool, really: an electricity usage monitor that tells you exactly how many kWh a device or appliance is drawing. The monitor can be as simple as a "plug load" monitor that plugs into an outlet; then you plug the device/appliance into the monitor. Typically, an LED screen displays the consumption.

One of the simplest, least expensive, and best known of the plug-load variety is theP3 Kill A Watt EZ, available atAmazon(Opens in a new window) and elsewhere. After the device pulls some power for a while, push some buttons to have the monitor auto-calculate how many kWh will be used in a day, week, month, or year, providing an instant estimate. It also measures the quality of your line. It won't necessarily work on all appliances, especially items like electoral dryers or hot tubs, because it's for use on 110 to 120 volt systems—not 220V and 230V like you'll findalmost everywhere else on Earth(Opens in a new window).

(Video) How To Measure Power Consumption At Home

How to Measure Home Power Usage (3)

More advanced versions, like theKill A Watt Control(Opens in a new window), not only monitor usage, but can be set with programs to turn on and off to save electricity on your pre-set schedule. The Control has backup batteries so if you disconnect it from the outlet, it'll hold all the info already recorded.

If you've got a smart home, there are a number of smart plugswith built-in energy monitoring, including our Editors' Choice picks, the Belkin WeMo Insight Smart Plug and ConnectSense Smart Outlet 2.

If you want whole-house electricity monitoring tools, there are several systems. They work via sensors placed on the lines (usually at the household junction box); the sensors then talk wirelessly to meters and gather lots of data, usually uploading it to the web for you to access. Some should beinstalled by an electrician(Opens in a new window), but there are a few that are sold with the promise that anyone can put it in. Examples include:

  • $349Sense Energy Monitor with Solar Tracking(above)
  • $349Eyedro Business Electricity Monitor. Eyedro also offers cheaperhome versions(Opens in a new window)down to $99 and up to $299 depending on if you want to support only Ethernet or Wi-Fi for monitoring, or add more sensors.

What's really cool is, a system like the Sense Energy Monitor isn't limited to just the whole house energy usage. It actually can pinpoint the electronic signature of every device drawing power and uses algorithms to ID them and point you to the vampires.

What to Do With Vamp Energy Info

So, you've got a list of all the products in your house that are plugged in, from electric toothbrush charger up to the refrigerator, and you know exactly how many kWh they utilize, and have extrapolated that number into the cost per week/month/year. What's next? That's up to you.

(Video) How to Monitor Electricity Use | This Old House

Some items you can't unplug. Like the garage door opener or the fridge or the hot tub. Not even to save cash, unless you want to be stuck outside, have warm milk, and/or take a tepid tubbie with the hubbie.

However, there are devices that use the same power in standby as they do when powered up and they MUST be shut off for power-based peace of mind. A perfect example: that ancient fax machine your husband won't get rid of. Or any old appliances, like the answering machine on your old landline (just get Google Voice(Opens in a new window) already). Your microwave oven isn't drawing a lot of power by sitting there, but that clock on the front costs you even when you're not cooking. Same goes for your coffee maker, toothbrush charger, and air conditioner. All those little lights on the front have to require current.

Smart plugs and power strips are the best way to take control. You can then put your smart home hub or smart speaker to work helping you power-off the insurgent vamps. (Over the holidays, it's a great way to make sure the Christmas tree and ancillary decorations don't stay on all night, Clark Griswold.) You can also find some specialty helpers like P3's Save A Watt TV Standby Killer(Opens in a new window), which has one job: Turn off power to TVs in standby mode. And don't forget the bulbs—smart bulbs, or at the very least a switch to LED bulbs, will make a big difference.

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(Video) How Installing Sense to Monitor Electricity Usage Saved $100/Month with Dedicated Circuit Monitoring

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How can I measure the power consumption of my home? ›

To calculate power consumption of any appliance, you have to multiply it's wattage by the number of hours it is being used (operational hours). For example, a 1000 watt electric iron running for one hour will consume (1000 watt X 1 hour) 1000 watt hour or 1 kilowatt hour (kWh) of electricity.

How can I find out what is using so much electricity? ›

How to find which appliance is using too much electricity? The most reliable way to find this out is to get an electricity usage monitor. It'll tell you exactly how much electricity a device or appliance is using. Just plug the monitor into a socket and then plug your appliance into the monitor.

Can I monitor my electricity usage without a smart meter? ›

An energy monitor provides a way for those without a smart meter to keep an eye on their energy usage.

How much power does a house use in 24 hours? ›

If you divide 10,715 kWh by 365 (days in a year), you'll get the average number of kilowatt-hours used per day, which is 29.36 kWh. If you multiply that by 1,000, you can find the energy consumption in watts that occur in 24 hours, or 29,360 watts.

How many kWh per day is normal? ›

What's the average home power usage per day? In 2019, residential customers in the United States purchased an average of 10,649 kilowatt-hours of electricity. This works out to be roughly 887 kilowatt-hours per month, or about 30 kilowatt-hours per day.

How much electricity does a 2000 square foot house use? ›

Home Professionals lay this out clearly stating that “the average 2,000 sq. ft. U.S. home uses around 1,000 kWh of energy per month or about 32 kWh per day.” But again, it's not so clear cut. The U.S. Energy Information Administration notes that the average homeowner used about 914 kWh per month in energy.

How do you check which appliances use the most electricity? ›

The wattage of most appliances is usually stamped on the bottom or back of the appliance, or on its nameplate. The wattage listed is the maximum power drawn by the appliance. Many appliances have a range of settings, so the actual amount of power an appliance may consume depends on the setting being used.

What causes high electric bill? ›

The most common cause of high electricity bills is simply that you have used more power in the home than you thought. This could be due to the season, for example – have you been turning the air conditioning on more during a mini-heat wave or your electric radiators to deal with a cold snap?

Can an oscilloscope measure power? ›

Depending on the waveform math capabilities of the oscilloscope, these measurements can include instantaneous power, true power, apparent power, and phase. There are two primary types of current probes for oscilloscopes: AC current probes.


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