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My Electric Bill Was WHAT?!? Analyze Your Power Use with These 3 Web Sites

The views expressed are those of the author and are not necessarily those of Scientific American.

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In one of the best quips I’ve ever heard at a scientific conference, cosmologist Max Tegmark complained about a lecturer’s vagueness and pleaded for some quantitative predictions: “numbers—you know, the kind with decimals in them.” Like Tegmark, I love data. Concrete information beats hand-waving speculation any day. So it’s awfully fun to use a home energy monitor to track your household electric power use in real time. Practical, too. Knowing how much you spend is always the first step in figuring out how to save. Studies show that people who have home energy monitors find ways to cut their electric bills.

Over the summer, data-lovers suffered a blow when Google pulled the plug on its Powermeter website, which provided a convenient way to track your home’s electricity use. But shortly after I bemoaned its demise, I learned about several other sites that are in some ways even better. They not only display your power consumption but also analyze it for patterns that could help you save money.

To collect the data, I have a unit called The Energy Detective, which consists of a pair of sensors that you clamp around the main power cables in your circuit breaker panel. Other systems, such as those by Blue Line and WattVision, attach to your utility electric meter. All take power readings and keep a running tally you can view through a web interface or mobile app. Lots of other devices are other there—energy blogger Chris Kaiser keeps a comprehensive list—but not all can upload the data to external analysis websites.

Those sites crunch the data and give you a breakdown of where the juice went. They rely on the fact that each appliance has a telltale pattern of power demand. A fridge, for example, regularly cycles on and off—you can easily see it on a graph of your total household power consumption. In principle, the analysis algorithms could go a-huntin’ for power hogs such as broken appliances and family members who crank up the a/c when you turn your back.

Unfortunately the TED monitor can work with only one external website at a time. PlotWatt had the cleanest interface, so I decided to give it a go first. You type in some general information about your house, such as how many of which types of electric appliances you have, so the algorithm knows what to look for. The site said it would take a week before it had enough data to perform an analysis. A week went by, then two, then three. Emails to tech support went unanswered and, out of frustration, I tracked down the email addresses of the site developers, who apologized and said they’d been swamped by people migrating from Powermeter and another soon-to-be-defunct site, Microsoft Hohm. After a month, I finally got some results.

The level of detail was somewhat disappointing—I was hoping for a finer-grained breakdown, revealing patterns I wouldn’t have expected. Still, PlotWatt correctly inferred that window a/c units were our biggest energy sink. On the chart, you can see demand ramp up because of the midsummer heat wave. Our solar panels covered only about half my total demand over this period. Previous summers haven’t been so extreme and we usually don’t even put in the a/c until August. You can also see flatlines where the TED stopped sending data and had to be rebooted.

After putting PlotWatt through its paces, I reconfigured my TED to upload data to another site, EnerSave, and began to wait again. This time, it took two full months—I got my first results only two days ago. And they disagreed with PlotWatt’s. For the one load that should be fairly constant—the fridge—they differed by a factor of three.

One reason may be that, unlike PlotWatt, EnerSave does its analysis on net consumption—it doesn’t add in the solar power generation to get our total consumption. When I signed up, I asked the developers about this and they claimed that net consumption would be enough to detect patterns. Later, though, they backtracked. They said they are still tinkering with their algorithm, so I’ll let it run a bit longer before I switch to a third service, MyEragy, and try it out.

The EnerSave user interface has the distinct advantage of showing you exactly when the algorithm thinks certain appliances cycled on and off. This is revealing not so much of our power habits, but of the limitations of the algorithm. For instance, the graph shows that on August 27th, the room a/c ran almost continuously. That makes sense: we were starting to get water in our basement from Hurricane Irene and the dehumidifier (which registers as a/c) ran all the time. But the graph also suggests that the dehumidifier cycled on and off over the subsequent week, whereas in actuality it ran almost continuously until our basement dried out.

Clearly, these are works in progress. A more reliable way to get detailed data about your power consumption is to attach a hardware sensor to each appliance. Some energy monitors, such as EcoDog and eMonitor, do just that. But they are much more expensive and I personally can’t justify the extra cost. Love of data has its limits.

Screen shots by George Musser

George Musser About the Author: is a contributing editor at Scientific American. He focuses on space science and fundamental physics, ranging from particles to planets to parallel universes. He is the author of The Complete Idiot's Guide to String Theory. Musser has won numerous awards in his career, including the 2011 American Institute of Physics's Science Writing Award. Follow on Twitter @gmusser.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. jamesian 9:22 pm 09/29/2011

    University of Washington researcher Shwetak Patel has designed a new class of low-cost and easy-to-deploy sensing systems for the home, called Infrastructure Mediated Sensing, which leverages existing utility infrastructures in a home to support whole-house sensing. To allow residents to track their energy usage down to the level of individual appliances and fixtures, Patel’s distinctive approach leverages existing infrastructure — such as gas lines, electrical wiring, plumbing, and ventilation ducts — and requires only a minimal number of small, wirelessly connected sensors attached to the central hookup of each of these utility sources. When coupled with a machine learning algorithm that analyzes patterns of activity and the signature noise produced by each appliance, the sensors enable users to measure and disaggregate their energy and water consumption and to detect inefficiencies more effectively.

    Link to this
  2. 2. Dankanchor 6:37 am 09/30/2011

    I have the eMonitor and have had it for 2 years – and I’m saving about 20-30% of my electric bills. Why? Because I can now see everything in my house that uses electricity and how much it costs. I’ve basically been able to eliminate waste. I love the iphone app – which enables me from anywhere to see what’s going on in my house – room by room. When you say you can’t justify the cost, well if I am an example, I was able to pay for the eMonitor in just 8 months with the savings – so now there’s about $40-50 each month that I save that goes right into my pocket.

    Link to this
  3. 3. vuasite 1:33 pm 11/30/2011


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  4. 4. yfoam 9:08 pm 12/19/2011

    When coupled with a machine learning algorithm that analyzes patterns of activity and the signature noise produced by each appliance, the sensors enable users to measure and disaggregate their energy and water consumption and to detect inefficiencies more effectively.
    I think so.

    Link to this
  5. 5. heman800 9:25 pm 12/20/2011

    Did you all know that one bulb wastes 70% of energy and just 20 or 30% is light? We need to improve our technology and starts new laws on them. So sad here in Mexico happens to be illegal to own those pannels (for obvious reasons), and people with less money but produce more in their factories are the ones who could bennefit, I think we need a global law on this one, and to realize that many organizations will produce better.

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  6. 6. drbitboy 12:32 pm 03/1/2012

    Hey George,

    It’s all about the thermodynamics.

    Found this article and saw your name and said, hey, I know that guy!

    So you get to fiddle with stuff like this and then write about it on SciAm. Nice. Shouldn’t X10 be into this, which would make it cheaper and better?

    Take care,
    Brian Carcich

    Link to this
  7. 7. JamalBrown 4:00 pm 06/26/2012

    This has to be one of the coolest things ever. After I moved out of the house, my father called me to tell me how he has reduced the electric bill to $20 a month! AMAZING!

    My electric bill in Colorado was always about $120 a month and when I moved to Vegas, my bill shot up to $250 a month! That was the same amount I payed for rent!

    I visited CU-Denver and they had a guide on how to build a basic wind turbine at home. Very cool.

    Link to this
  8. 8. jwg01776 2:29 pm 03/17/2013

    EnerSave is now called “Bidgely” —

    Link to this

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