Five Percent: Conserve Energy

Climate Change Is Important: Energy Conservation is the First Step

September 18, 2009

Different Ways To Measure Electricity Use: Which is Right for You?

Category: Household,Save Electricity – Tom Harrison – 12:40 pm

As I have become aware of my energy use, I have grown more interested in understanding the details. I have used four methods to measure my electrical use:

  1. (actually) reading the electrical bill,
  2. using a Kill-A-Watt meter to measure usage of things we plug in,
  3. installing a PowerCost Monitor to display total house usage right in our kitchen, and
  4. installing a TED 5000 monitor that measures and records our usage in great detail

Each of these methods is effective, and each has resulted in incremental changes. For us, the incremental changes have added up: we now use less than half of the electricity we used to. Everyone can do at least the first of these — I hope I’ll show you why it makes sense to go a step further.

Read the Electric Bill

reading-glassesI started measuring my electricity use by actually looking at my monthly bill. By seeing how things changed from month to month, I was able to get an idea of how all of the changes we made helped. This is a very low-tech way of savings that costs nothing, and can be very effective — we reduced our usage by about 30%-40% using this approach.

Before this, to be honest, I just looked at one number: the amount I had to write a check for. Actually, I often didn’t even do this, because our utility offers electronic payment and also “level billing” — every month was the same, adjusting a little from year to year. I was completely unaware of the relationship between turning something on and it’s consumption of electricity.

One of the first things I did when I started writing this blog in 2005 was to figure out how to read the bill. The number that matters is killowatt-hours (kWh), and if your bill has it, average kWh per day, which evens out for billing cycles that are longer or shorter. And it turns out that our bill also has the numbers from the previous 13 months. Who knew?

As I began to read the bills, I made changes — I could see the net effect of those changes in next month’s bill … kind of. Our usage tends to vary seasonally. We used more in the winter months when it gets darker earlier, and of course the aquarium heater is on more of the time to keep our fishies a warm and toasty 80°. And we used more in the summer when it was hot and we ran the air conditioner. These seasonal changes are hard to separate from more general changes you might make (e.g. changing to CFL bulbs, making sure your computer sleeps when not in use, and so on. This is why it’s nice to compare usage to the same period the prior year.

We started seeing reductions every month as new things to change occurred to us. But the electric bill rolls up a month of actions into a single number, so it’s a little bit removed from any specific change. There was no financial investment to use this method, but we saved a pretty significant amount every month after a half a year of making a little change here and there.

Use a Kill-A-Watt

Kill-a-Watt Meter

Kill-a-Watt Meter

The Kill-A-Watt goes between anything you plug into the wall and the plug and has a little meter that displays interesting information (like watts) right then and there.

I had my TV, DVD player, cable box, stereo and TiVo player all plugged into a power strip, so I unplugged the power strip, plugged the Kill-A-Watt into the wall, then plugged the power strip into the Kill-A-Watt. After I figured out how to use the display, I was shocked: even with the TV off, this setup was using hundreds of watts — something like 325W, if I recall — and that’s with everything “off”. Well, the cable box was on, and the TiVo wants to be on all the time. But everything else was off. Or was it.

In a matter of minutes, I found the culprits, just by plugging in one device at a time. It turns out that the Motorola cable box was a complete hog, running something like 150W — for what? And the other secret sucker was my stereo, which was turned “off” — but it turns out that it has the ability to play music in multiple rooms. If you have the tiny little black-on-black buttons pressed in, a tiny little light on the front lit, telling me (apparently) that it needed to use 50W or so for each button. Doh!

Those two little buttons were costing me about $200/year in electricity.

Inspired by this success, I went around and found all sorts of little surprises. Our terrible wireless phones had old-style “vampire” transformers that were hot to the touch, and were sucking 12W each full-time. The speakers on our computers were always on, and it turns out the computer didn’t go into standby mode properly, and on and on.

The Kill-A-Watt helped me find all these seemingly innocent devices, and over time, I came up with ways to not have things on when they weren’t needed.

But not everything plugs in, and some are hard to get at. And the Kill-A-Watt is a cool thing to use from time to time, but, well, you have to use it.

We did use it, and by now, our electricity bill was regularly running at about 40% less than the prior year. That’s a lot, given that we were paying around $200/month in bills before. We were very proud of our accomplishments, and felt like we had done just about everything there was to be done. Ah, but that turned out not to be so!

PowerCost Monitor Real-Time Display (or TED 1001)

Not Really the Cent-o-meter

Not Really the Cent-o-meter

Thinking we had saved most of what we could, it seemed a little painful to shell out $100 to buy one of these gizmos. The BlueLine PowerCost Monitor has a part that clamps on to your electric meter, and reads the meter every few seconds, then transmits that information wirelessly to a little display we have in our kitchen. You can set it up to know what your electricity rate is, and have it display your cost in dollars, or just display kW.

Having the meter right in our kitchen was an eye opener. It’s just there, and like the clock or thermometer, you just glance at it from time to time, and get to know what’s normal for your house. Ours would settle down to about 500W to 600W when we had all settled down for bed, and that seemed find to me — the real surprise was just how much things like the electric dryer actually use — a load would run for about an hour, and used 6500 Watts. Man, that really could add up. We also realized that the kids did know how to use the “on” button on the electric heaters we had in the basement … but not the off button! These would also use a lot.

And so we did a little thinking. I cleaned the dryer vent. We tried some different settings on the dryer. The biggest change happened when we had to replace our washing machine and got one of the energy-efficient models — yes, the washer itself used a bit less electricity, but it has a spin-dry mode that gets the clothes far, far, dryer than our old washer, so now the dryer ran only about one-half as long. And we found ways to make sure the kids remembered to turn off the heat when they were done in the basement.

Just by having the reading in my face, we saw how we actually used this service that was formerly almost invisible. But I wasn’t done — our what was it that used 500 or 600 watts all the time? Time for a little more detective work.

One of the changes was to get rid of the computer “server” we had in our closet that was supposed to do great things like let us play music from cool players installed anywhere in the house, and be a central file server for our several computers, and other geeky stuff like that. I found an alternate solution, and chopped off 108W. I found out that most Windows computers will not go into standby or hibernate automatically, even after you fix them so they do … for a while. We eventually just got used to doing it manually. And power-strips — even when the computer is off, all those stupid wall-wart transformers are at the ready, sucking a little power, here and there.

By watching, looking, and changing where possibly, our baseline use is now running at about 200 Watts, 300 when the aquarium heater is on. I am pretty sure I know what is using those watts, and I have decided for now, that they are worth the cost.

The real-time monitor is an incredible thing. I guess you have to be a little motivated — for me, it’s just a fun thing to see how low we can go. And I continue to be surprised that there continue to be small ways to conserve, even after doing this obsessively seriously now for more than four years.

TED 5000

ted-5000-in-my-hot-little-handThere was one thing missing in the PowerCost Monitor — it mostly just shows you what you’re using now. But I am a computer guy, and a database guy, and I like to see how things change over time. The new TED 5000 provides this level of detail, recording, and remembering measurements from every few seconds for a long time. And its excellent software, which runs right in a web browser on your home network, gives you a picture that’s pretty incredible.

By looking at the graphs, you can easily see patterns that are associated with a particular device. I have my eye on our refrigerator — even at night when the doors are closed, it goes on quite frequently and runs for a pretty long time — it seems to be on about 20 minutes and off about 20 minutes; when on, it uses from 100 to 200 Watts; I assume it’s on longer during the day when its doors are getting opened and closed. This seems excessive to me.

Which Is Right For You

We are now saving something like $120/month on our electricity bill — using power at our old rate, we would have paid around $200/month, now it’s about $80/month. I have invested some money in CFL bulbs, Smart Power Strips, new appliances, and a decent amount of my time. I have also paid for the Kill-A-Watt and PowerCost Monitor (the TED was a gift from a like-minded friend). But the cost of all of these things together have long since paid themselves back.

All four of these approaches require only two things:

  1. A little effort and commitment to become aware
  2. A little effort and commitment, and sometimes a little expense, to make changes to conserve

So start with the first: read your electricity bill, and compare it to last month … every month. Challenge yourself, or better yet, challenge your family! It’s not hard, it doesn’t require great sacrifice, and it’s what we all need to be doing to help deal with climate change.


  1. Hi, do you know of devices like TED and Kill-a-watt that work well in the EU… Germany in particular? I’ve been following your site and it is nice to have one post that kinda summarizes some of the steps you’ve made.

    Comment by nathan — September 18, 2009 @ 2:38 pm

  2. Nathan — you may want to inquire about The Owl ( which is made for sale in the UK. I believe the Cent-a-meter is sold for use in Austrailia. I am not sure if either will work in Germany, although it looks as though the display configuration supports multiple currencies — a good sign :-)

    UK line voltages and frequency are the same as Germany (230V/50Hz), but I am not clear on how many phases (separate wires) come into the house to deliver the power. The other minor issue is the plug configuration for the part that powers the display — you might need an adapter for that.

    As far as the Kill-a-watt goes, I found one site claiming that you could use a voltage converter to reduce the output to the 110V supported by the North American standard.

    Please write another comment if you find any useful information about support for these items in Germany or other countries.

    Comment by Tom Harrison — September 18, 2009 @ 4:35 pm

  3. […] easy as small changes in lifestyle, neither expensive nor difficult. It’s quite possible to reduce your electricity use by half, for example. Solving global warming is more a political problem than a technical one, persuading […]

    Pingback by Why is Copenhagen important? | Song for Jasmine — September 19, 2009 @ 4:16 pm

  4. Hi tom,
    the OWL looks great. They do have a model for worldwide distribution. So it will work in the EU, and perhaps the US as well. It is rather cheap too, around 60€ to 70€. They say on their website they can only ship the USB data monitor inside the UK so I’ve asked them if there is another way to get data logging with the international model.

    In addition, wikipedia links to a couple that will work in the EU. The most sexy of them is the Wattson which goes for 150€. It also features long term logging like TED or OWL. See this video (in dutch but pretty self explanatory) or .

    There is also the Eco-Eye which I found sold here in Germany for 100€ (and other places in the EU)

    But, the option I’m probably going to use is the Flukso open source monitor. This is basically a microcontroller plus an open router, I think. All of the source files for fabricating a board are available. I took a look at the source and it is actually using some Arduino libraries so I imagine this can all be built using the super-simple arduino prototyping platform. It also supports data logging. Did I mention its all open source :)

    Comment by nathan — September 21, 2009 @ 10:16 am

  5. the nice thing about going the open source route is that I can try to implement a feature missing from all of the energy monitors. When you look at your data and graphs you start to wonder what devices were causing the load at a certain point. Eventually you start to make note of the hogs, oven, fridge, etc. As you get a feel for you it you can quickly see in the graph when the big items are on. So why can the software do this for you? It could, actually. If you know the living room lamp takes 12-14 watts then if you annotate this in your data once the software could track whenever there is a total increase or decrease by this amount and tell you when the lamp was turned on, left on, turned off. Do this for all your known devices and you will a clear picture of what was on, even when looking at data a month old. The other nice part of this is that you could tie this information into a site like and create more accurate profiles for electrical items. You can also track degradation of efficiency for items over time, compare the efficiency of your items to others, etc.

    Comment by nathan — September 21, 2009 @ 10:39 am

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