Five Percent: Conserve Energy

Climate Change Is Important: Energy Conservation is the First Step

July 28, 2008

Cent-A-Meter, Centometer, or PowerCost Monitor: Pays For Itself

Category: Conservation,Green Reviews,Household,Save Electricity,Tips – Tom Harrison – 12:00 am

Not Really the Cent-o-meterI have a product, known variously as the “centometer”, “cent-o-meter”, “cent-a-meter”, “powercost monitor” and “power cost meter”. It shows your electrical consumption in dollars and cents on a little display you can put where you like. Your electrical use is no longer “out of sight, out of mind”.

Update: 3/10/2009 — the same unit is now being sold under the Black and Decker label.

And boy does it work!

I bought one and installed it, and, having received our first electricity bill since then, can confidently say that it will pay for itself in less than a year. Maybe a lot faster than that!

Update, 2009: Oh yeah, a LOT more quickly than a year!!

Where To Buy The Cent-a-Meter

I’ll call it the Cent-o-meter, because the TV show Wa$ted used that name. The model I got is officially called the PowerCost Meter, and I purchased it at the TerraPass Store for $134. Update, 2009 — BlueLine’s PowerCost Monitor is now available for about $100 at Energy Circle’s store

I found the “real” Cent-A-Meter online for $153. I have not used the actual cent-a-meter. They should both have the same result, even if they work a little differently.

Does that seem like too much to spend?

Is the Cent-A-Meter Too Expensive?

Consider that over the course of several years, my family and I have reduced our electricity use by more than 40%. Our bill this month was around $100. Our electricity rate, like those around the country, will be going up (way up). This month, we appear to have cut yet another significant percentage off our total, I think now up to 50% reduction. In other words, our bill last month would have been $200 without our conservation measures.

So if you are starting from scratch, you could easily get the first 25% in a few days, using the Cent-o-meter as a guide. In our house, that would be $50/month. Maybe you’ll get more, or maybe you pay less for electricity (now), but it won’t take long to pay for itself.

How We Cut Our Electricity Use in Half

We learned how to save electricity usage the hard way: try a things or two, wait for the electric bill to arrive, and see how we did. This method takes discipline, patience, diligence, and perhaps a mental disorder (of which I have all, except perhaps patience :-). Yes, I could have walked outside, read the electric meter, done the math, and all, but I didn’t. I’ll bet you don’t, either.

I was aided in some cases by my Kill-A-Watt meter, but that only works for things you plug in, run on 110 volts, and can reach easily. For us, this did not include the dryer or our fridge, nor most of our lights.

It took a long time. Some things, like turning out lights you aren’t using take a lot of practice. It would have been a lot quicker if we had this little display sitting in our kitchen all along, right next to our thermometer and clock.

You Know When The Dryer Is On

The PowerCost Meter works because you know within a few days what really uses electricity in your house.

When things are mostly quiet, we still use about 5 or 6 cents per hour — a dollar a day. When we’re up and about, it’s usually around $0.12 per hour; lights are on, the refrigerator is running, the computer or TV is on, and so on.

Here’s a picture from this evening — $0.09/hour, we have used $22 of electricity since I last reset and it is surprisingly cool 64 degrees outside for a late July evening.

But when I look down and see $1.22 per hour, I know the dryer is on. Holy cow!

Why Does The Cent-o-Meter Work?

In truth, it’s not the actual money that motivates me. I waste a lot of money on a lot of other things less useful than dry clothes. I know having a clean dryer vent can significantly reduce drying time, and now I feel more motivated to keep it clean. And fewer loads seems like a better idea. And I wonder if it would be practical to dry a few things on a clothes line?

The same idea works in my car (a Toyota Prius). Being aware of my mileage at any moment has affected my driving habits only because I am immediately aware of the gas mileage impact of how I am driving. There is no doubt in my mind that I am currently getting 51.9 mpg in my Prius, well over the rated 45 mpg, because I pay a lot of attention to that meter. It’s something to do, and kind of fun.

Installation and Stuff

The model I got (BlueLine Innovations PowerCost Monitor) installed easily in about 20 minutes. It has a device designed to be strapped around the electric meter, and it actually reads the meter. It can work with most common meters, even the old spinning-dial ones. Instructions were good, and there’s a special book for each different meter kind.

The meter-reader part has a wireless transmitter that sends a signal to the display part that you put inside your house. You set the date and time, and also, using a current electrical bill, enter the amount you pay for a kilowatt-hour of electricity, which is usually right on the bill. That’s all.

The actual Cent-a-meter works slightly differently — rather than being strapped to the electric meter, you wrap a measuring device around the main electricity wire to your house. Other than how they get at the usage, both devices seem pretty much the same.


  1. What is the range of the wireless?

    [Our meter is in a basement, and our primary living space is on the 3rd floor; a long throw for most wireless devices.]

    Comment by john — July 28, 2008 @ 7:15 am

  2. John —

    This evening, I took the reading unit out for a walk. I was at least several hundred feet away from the sending unit before the signal strength meter started faltering. I also walked around so there were several houses in the way; still 5-bars signal.

    The unit seems to have some smarts, too; it if fails on one read it will keep trying. Unlike wireless phone or network, a tiny bit of data needs to get sent every few seconds — hardly a challenge.

    Unless you live in a castle with lead-shielded walls, I would bet you’ll be ok :-)

    Comment by Tom Harrison — July 28, 2008 @ 8:13 pm

  3. Thanks for your review Tom! My husband and I have been gradually taking steps to reduce our power useage and simplify our home and this is one of the next things I was considering. Its tough to balance what’s actually helpful in your home in the long run with the recent boom of “green” consumer goods. We live in South Waltham in a 100+ uninsulated house, so anything we can do is a big help. Baby steps! :)

    Comment by Jodi ("Dancer" in Livejournal) — July 30, 2008 @ 12:06 pm

  4. Jodi —

    It’s true, insulation is almost always the most cost-effective first step. Our house is old, too, 1910 vintage, and we had cellulose insulation blown in some years back. They took the clapboards off a few rows of the outside which was a bit of a mess outside, but caused minimal disruption inside. It really wasn’t expensive, and considering how much we have saved since then, it looks like a great deal.

    Today, I might have gone for the expanding foam which needs only tiny holes, and may do a better job insulating, especially in older houses which tend to have various bracing and fire blocks that can get in the way of blown-in insulation. There are a few spots in our walls we can feel in the winter that are cold to the touch.

    But if money’s tight, simple steps like caulking around windows, feeling for droughts, and covering up the big gaping holes can be a great first step. Another no-brainer we did was to get a programmable thermostat, which took all of 10 minutes to install, and keeps the house at the right temperature all the time.

    And don’t forget all the other little things. In fact, forget the “big things” and focus on the little ones that are free. You’ll save enough money in a few months to pay for insulation, new windows, and a gold-plated Prius!

    Seriously, check out the various Energy saving tips here and you’ll certainly find a few that are simple, cheap, and easy to do.


    Comment by Tom Harrison — July 30, 2008 @ 8:41 pm

  5. Thanks, Tom!

    Comment by john — August 3, 2008 @ 4:05 pm

  6. Do you know if anything like this exists that can send a signal to a computer, and map trends? Or store the hourly info so we can download and map trends? I think I could help my family be more effective in reducing waste if we could determine what our worst times are. Particularly if I could say “even when we sleep, we are spending “x” amount of money each hour.” Thanks for this wonderful show. I have learned so much!

    Comment by Vicki — August 17, 2008 @ 7:32 am

  7. Vicki —

    After I first got the PowerCost Meter (Cent-a-meter) a friend at work said “If this thing has a wireless protocol, you need to figure out what it is saying and write a web interface to record it”. He is even geekier than I … and so are you :-)

    So it’s true that this data is available in some form via the Internet, but as far as I know no one has yet written a web-based interface to the data stream.

    Hmm — perhaps I have a little geeky thing to do after I return from vacation :-)


    Comment by Tom Harrison — August 18, 2008 @ 10:52 pm

  8. […] PowerCost Monitor (which measures all the electricity we use) reports that we’re using about 400 Watts of power […]

    Pingback by Two More Big Electricity Savings (Thanks, Apple!) | Five Percent: Conserve a Little Energy — September 14, 2008 @ 7:22 pm

  9. […] and probably most important of all: bought a PowerCost Meter […]

    Pingback by Save Electricity — Our 45% Reduction Saves $1,250/year (Updated) | Five Percent: Conserve a Little Energy — September 19, 2008 @ 12:47 pm

  10. Oh yeah, baby, another electricity bill from NStar … and, drumroll … 32% year-over-year reduction on my latest bill.

    Last year in the same period we used 22.0 kWh/day, this year 15.0 kWH/day. At our electricity rate, we saved about $33 on our bill compared to last year.

    I really wish I had one of these things for our gas and water meters!

    Comment by Tom Harrison — December 7, 2008 @ 4:52 pm

  11. I REALLY want to get one of these.

    Comment by Mr. Green Gear — January 6, 2009 @ 11:29 am

  12. […] I installed our real-time PowerCost Monitor, we were able to measure our total electrical usage and see how what we did used electricity. It […]

    Pingback by Measuring It All — Beyond Electricity | Five Percent: Conserve a Little Energy — January 23, 2009 @ 7:58 pm

  13. […] and extremely effective efforts to reduce the amount of electricity we waste, we can look at our PowerCost Monitor and see that when we’re not running the dishwasher or dryer, and have a few lights on, we use […]

    Pingback by Become Aware with WattzOn | Five Percent: Conserve a Little Energy — January 25, 2009 @ 8:37 pm

  14. […] house, we dry about 4 loads per week. It takes about 1/2 hour per load, or 2 hours a week. Using my PowerCost Monitor, I can see the dryer uses 7500 Watts when the heat’s on, and 200 Watts when just tumbling, […]

    Pingback by Saving Lots of Watts by Sleuthing | What's on? — February 4, 2009 @ 4:01 pm

  15. Hi,

    I would like to have your recommendation on which product(s) will better serve my specific needs…

    I will sub rent 18 apartments (now in construction phase) to different tenants and only have one single Power consumption measuring unit, the one from the electric company… i can probably have a second feeding line with a corresponding second meter from the electrical company… every time i get an electrical bill I need to subdivided proportionally according to everybody’s consumption to charge the electrical cost to all tenants…

    I have a 3 wire feed to each apartment phase 1, phase 2 and ground so each apartment has 220 ACV as well as 110 ACV.

    I need to measure the consumption for each apartment during a specific time fame (to mach the electrical bill dates)

    Each apartment has one air conditioning unit at 220 ACV and 110 ACV that supply 5 outlets and 2 or 3 ligth bulbs (topically a fridge, a microwave, a computer, a lamp and a TV set are connected)

    by doing this i hope to achive that every tenat save as much energy as possible if not because a planet concern at least due to a cost concern as opose to the common practice at most hotel rooms in wich people tend to live the air contidioning on all day long…

    Please help me to select the best measuring device…. if further information is needed from my end please let me know

    Thierry Brunet

    Comment by Thierry Brunet — March 10, 2009 @ 12:38 am

  16. @Thierry —

    If you would like to send bill you tenants separately based on their electrical consumption, it’s a matter of money, you will need a meter that everyone agrees is the authoritative measurement. It was a long time ago, but I used to work for a residential property management company — at the time, the only solution for this was to have the electric company install separate meters, and most likely, have the tenants pay their own electricity bills. Perhaps this isn’t what you’re looking for — if it is, it’s expensive.

    So I’ll assume you want to help tenants understand how they are using electricity in hopes that it will help them know how to use it more effectively.

    The device I wrote about here will not work, as it attaches directly to a (single) meter. There are several other devices which measure power flow by induction — a device wraps around the incoming circuit wires and measures current.

    However, in the US, the only one of these I could find is called The Energy Detective (TED). This device is about the same price as my meter, and has an option to record the data it collects to a computer via a USB interface and some software.

    Another induction measuring product called The Owl is considerably less expensive, but appears to be sold only in the UK. As far as I can tell, there’s no reason it wouldn’t work for any power system (I have sent them an email asking if there’s any reason it’s not sold in the US or Canada).

    In both cases, you would need one of these for each unit in your building. The displays are all powered by AA or AAA batteries.

    Other meters are available — one source I found is the PowerMeterStore — there may be some options there that are right for your application. (Update — check out this ELF Panel Meter which seems designed to do exactly what you’re looking for. There may even be volume pricing.)

    I am very interested in what other solutions you may find, as this kind of real-time metering that is one of our first steps towards a smarter energy grid. Please let me know if you find anything!


    Comment by Tom Harrison — March 10, 2009 @ 7:19 pm

  17. […] You could have a real-time meter of which appliances are using how much energy (kind of like the PowerCost Meter that I use in my house now, but much more elegant, simple, and detailed). Check out the Zigbee site […]

    Pingback by Smart Meter, Meet the Smart Grid | What's on? — May 6, 2009 @ 4:13 pm

  18. […] have installed an ancillary meter that provides near-real-time usage data via a wireless display monitor in our kitchen. Our device is designed to read data from the electricity meter at our house, using […]

    Pingback by Electricity Data: The Devil is in the Details | What's on? — May 26, 2009 @ 5:17 pm

  19. […] while going from a dumb electric bill to the PowerCost Monitor is a big step, it certainly has its limitations. For me, the most difficult aspect of the device […]

    Pingback by TED 5000: A Big Step for Smart Metering | Five Percent: Conserve a Little Energy — June 1, 2009 @ 9:47 pm

  20. […] using at the moment. The TED 1000 series did that, and is very similar in function to my PowerCost Monitor from Blue Line (same one as now sold on the Black and Decker […]

    Pingback by TED 5000 (The Energy Detective): Released, and I Have One | Five Percent: Conserve a Little Energy — August 21, 2009 @ 3:03 pm

  21. How do you measure the total dollar amount used if the electric company bills the kilowatts used in different tiers? Is this something that can be programmed onto the unit?

    Comment by Patrea — November 3, 2009 @ 5:29 pm

  22. The PowerCost Monitor and similar devices like the ted 5000 understand several tiered rate structures and let you enter the data. Works great! Both at available at Energy Circle and other stores on the web.

    Comment by Tom Harrison — November 4, 2009 @ 12:47 pm

  23. […] to find ways to reduce our electrical consumption by about 40%.  All of this was before we got our first electricity monitor, the BlueLine PowerCost Monitor.  Then I got a TED 5000 about a year ago when it first became […]

    Pingback by Energy Monitoring: It’s Not a Passive Thing | Tom Harrison Jr — August 26, 2010 @ 12:51 pm

  24. Take a look at It works on all the branch circuits and you don’t need to jump up and run around. It can log it all and get to the bottom of it in a week. It also helps with power factor that can be a stubborn chronic loss.

    Comment by Chris Clement — April 9, 2011 @ 5:59 pm

  25. I have had a Cent o meter Owl for many years and do look at it but could do more but it is mostly for interest.
    On the Owl it has the option of showing gm CO2 per hour based on a conversion.
    I am working on a different project now
    Can you confirm the NZ standard conversion from kW-hr to gm CO2

    Comment by Bob Baker — September 6, 2011 @ 7:09 pm

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