Measuring the Energy You Use?

centdollarman asks: "Everyone keeps talking about how energy is being wasted here and there. Energy bills keep soaring for me, and now I'm back to paper and pencil: just taking notice of the power meter values. Mine is nice, as it has a cute LED that blinks at 1/1000 of a KWh. However, there has to be a better way to do this, and I've started searching the web for someway to count my usage, automatically. Of course, this is easier said than done. It would also be nice to have some way to (cheaply!) measure the power consumption of a single device." So, for the energy conscious among us: how are you measuring the power you use?

Comments

Stating the obvious

[iainl]

Don't you have meters anywhere you could keep an eye on?

Extensive tracking on a per device basis is probably going to use up energy itself, so I'm really not sure if that bit will achieve too much.

Weird units

[QuantumFTL]

blinks at 1/1000 of a kWh

In these parts, we call that a Watt-hour. What are you, some kind of Canadian?

Re:Weird units

[Anonymous Coward]

You have Wh in the US? I thought you measure energy in ounceyards or something like that?

Re:Weird units

[Schraegstrichpunkt]

Every time a watt-hour (3600 Joules) is consumed, an LED blinks. What is your problem?

Re:Weird units

[Keebler71]

Obligatory Grandpa Simpons quote: "The metric system is the tool of the devil! My car gets 40 rods to the hogshead, and that's the way I likes it!"

For an individual device

[keithmo]

http://www.thinkgeek.com/gadgets/electronic/7657/

Re:For an individual device

[djmurdoch]

The Kill-a-watt has a pretty bad user interface:

  - It is big, so it blocks both parts of a duplex receptacle if you plug it in directly. Use it on a small extension cord.

  - It is powered by the source you plug it into, with no retention of results when unplugged, and no light on the display when in place. Bring a flashlight and/or a longer extension cord if you're using it behind an appliance.

But in a well lighted location, it is quite informative.

Re:For an individual device

[subreality]

That's why we have the Watts Up Pro: http://www.thinkgeek.com/gadgets/electronic/7acf/ . It even has an RS232 interface. But it's relatively expensive.

I have a Kill-A-Watt, and it has all the problems you mentioned, but it also does everything it promised to do, for cheap. I'm quite happy with it.

Re:For an individual device

[ObjetDart]

Another satisfied Kill-A-Watt owner here. The above mentioned limitations haven't really bothered me. So far I've used it to learn the following things:

• All the devices in my home office together are costing me about $35/month to run
• Just running the World Community Grid Agent (or any other distributed client that maxes out the CPU) causes my 2 PCs to use an extra 50 watts/hour each...which at our very high electricity rates costs me an extra $12/month
• The dehumidifier we have in the basement is a vicious power sucking beast.

Datacentre

[IckySplat]

The Datacentre we have our kit in has these small LED based ammeters on each of the power strips.
Very handy for figuring out where our power budget is going.

Google provides the following in quick order
http://www.energyoptimizersdirect.co.uk/acatalog/E nergy_Devices.html?gclid=CJ2il5S3r4cCFTpsEAod3n1L- Q
http://www.blackbox.com/Catalog/Detail.aspx?cid=18 3,1324,1328&mid=4084

Enjoy :)

Conserve it anyway first

[arun_s]

1. Switch off your computer when you're not using it. (unless you're running a really important server or something. SETI@home does not count.
2. Switch off the lights when you leave a room.
3. The TV doesn't need to run all the time.
Every little bit helps. If you're already doing stuff like this & you're bills are still soaring, then you can try the measurement parts.

Re:Conserve it anyway first

[Anonymous Coward]

Every little bit helps.

I hate statements like this because they aren't logical. I'm not saying that it isn't logical to save energy, only that a shotgun approach is not the most logical method. If you want to save energy it would probably help to look at the items in your house that use significant amounts of power. While it may make you feel good to turn off a 40W light, it isn't going to make nearly as much difference compared to raising the temperature of your refrigerator, using your washing or drying machine less, using your microwave less, using your hairdryer less, using your oven less, or raising the temperature of your thermostat (or decreasing for the winter). Each of the latter is a KW magnitude device.

The best way to save energy is to prioritize. Work on thermal insulation and sealed windows will probably pay back twice the energy savings to what the energy nannies around the world recommending you turn off your lights, TV, and computer. The reason should be obvious for those with electrical heating: since electrical energy will eventually become thermal energy, does it make a damn bit of difference heating a home by electric heaters or by your TV, stereo, computer, and lights? Why limit them if your thermostat is at the same setting? Local effects? Then buy a fan (and the same argument still applies).

What would be the effect of limiting your lights, TV, and computer use if you have electrical heating? Your heating system would have to compensate and operate longer to reach the setpoint on the thermostat. In effect, if you live in a cold place there is no purpose to reduce other electrical loads unless they overcompensate for your heating. In a hot place, it makes sense to limit your other loads, but prioritizing will have a larger effect.

But since we are talking strictly about energy usage, household electrical power really is just a drop in a large bucket. Your car will be at least 200 KW thermal, and local industries will outpower residential electrical usage by over a 2 to 1 factor even in rural communities. I came from a town of 30,000 people. Residential areas used from 30-60 MW. One local mine used 50 MW (open pit mine with ore crusher). Another local silicon manufacturing plant used from 30-60 MW.

well,

[joe 155]

I agree with some other comments about conserving energy as a good way for going and stopping your bills from going up... as for a way of measuring you can see that kill-a-watt device some people have shown, it seems like a good idea. One issue is that it doesn't really tell you how much power things like lights and your oven use though (because they don't have standard plugs - at least not here).

The only way I can think of doing that, although it would be a hastle, would be to switch off all items in your house and verify that with your little light not blinking, then switch your oven on and time how long it takes you to use a Watt/hour. Then switch that off and see about the lights you would normally have one. This would give you some ideas on how much these things use. As a way of reducing the amount of power that they use you could get energy efficient bulbs (they cost more innitially but less in the long term) and if you need to replace your oven you can look for the most energy efficient one you can find (and if gas or electric is cheaper in your area angle your purchase towards that).

There are also good savings to be made by changing your fridge/freezer and your washing machine to something more efficient (If you live in England we already have a rating service for these, buy only A rated things and you'll save - if not then you'll have to do some investigating on your own)

Re:well,

[joe 155]

well we can only really talk anecdotally but I find that they last a lot longer than regular bulbs, the standard lightbulbs are supposed to last for around 3,000 hours, and the energy efficient ones are supposed to last for 10,000 hours...

I suppose this comes down to if you can trust the manufactures and what they say. I agree about you with the warming up period, but it is only for a minute or so, and worth it in the long run (if you do indeed get the full 10,000 hours)

Re:well,

[sbryant]

... would be to switch off all items in your house and verify that with your little light not blinking ...

Take this a step further: plug your TV/HiFi/etc into a powerstrip with its own on/off switch. When you're not using the devices, turn the powerstrip off, and get used to always doing that. Then you'll be using exactly zero Watts! European electronic devices can normally be switched off (in addition to any stanby modes), but it seems that this is not the case in the US. BTW: you can get powerstrips with surge protection, which is quite useful - I know two different people who have had computers damaged by surges (lightning induced).

As for the bulbs: turning the lights off completely saves even more than the low-power ones! It may sound obvious, but I've often noticed that people leave all sorts of lights on where it's really not necessary. Also remember: the low power bulbs' life expectancy has more to do with the number of times they are turned on than the total on-time, so they may not make sense for some locations; they don't work with dimmer switches either. Other than that, they're a very good idea, and I can now get ones that are the same shape as the old-style bulbs, thanks to a plastic cover over the tubes.

I think the energy ratings for fridges and the like are at least a European standard. We have them in Germany too. The downside of a highly efficient fridge is that you may end up pulling the handle off, because the vacuum inside is so strong!

-- Steve

Re:well,

[rhandir]

I've had good luck with the compact fluorecents in ouside (enclosed) fixtures. No heating/cooling cycles on a fragile bit of filiment has meant no bulb replacements in 1.5 years, as opposed to every 3-4 months. The light quality (color) is kinda iffy, but I'm willing to use them in the garage, basement, and kitchen. Heat dissapation is a bigger issue, the sockets in most of the fixtures in the house are cheap, and can't hold more than a 60w incandecent. This means that I can put the equivalent of 200w in an enclosed fixture in my kitchen, and I can cheat with y-socket adaptors in the basement without worrying about things melting. Definitely cheaper than upgrading sockets, let me tell you. Granted, I have pretty clean power where I live.

Insane measuring

[Jboost]

Take a look at this and see how he did it.

A infrared-sensor is optical connected to the flashing led on the electricity meter of the power company and reads the total consumption we use. The led on the meter flashes 480 times for every Kilowatt (kW). The pulse is counted by a Dallas One Wire counter with memory and once every minute my computer reads the amount of pulses (led flashes) counted. All the data is saved in a SQL database which I can query and display on the webpage's.

Electrical power is supplied and distributed around the Bwired house at 50Hz. However, the wires are actually capable of carrying a range of other frequencies which can be 'tuned-in' using appropriate equipment. Powerline technology takes advantage of this unused bandwidth of the electrical wiring in the home. The PowerLine device plugs into the electrical socket and draws power for the device. At the same time, it sends data signals down the power cord. A second PowerLine device can then be placed on any electrical outlet in the home/office to receive the signal. Now any Ethernet device (internet cable/DSL modem or another computer) can connect to the PowerLine Ethernet port and create a home/office network.

Re:cheaply measure a single device

[Myself]

I love my kill-a-watt but I've been thinking of picking up a Watt's Up? for the datalogging capabilities. But the price is silly, I should just build one.

Anyway, a clamp-on ammeter should be in your toolkit. (Get a DC-capable model and watch motherboard/peripheral power draw inside your PC!) Instead of slicing open an extension cord, consider an AC line splitter to make your measurements with. The 10-winding side makes small measurements more accurate, and it looks more professional if you end up using it on the job.

Re:I have a system that periodically updates me

[Anonymous Coward]

Turn off any computers that are unessential.

But this is slashdot, where unfortunately uptime is more important than power saving.

Easily said.

[SharpFang]

It's easy to say "switch everything unnecessary off".
Sure I do switch off the obvious things. Then still my bill is high. Then I check: The monitor (22" CRT) is rated at 40 Watt in standby mode. The ethernet switch is pretty hot. I have no idea how much the laser printer needs in stand-by, but likely not all that little. All these toys plugged into the USB hub, do they remain off when I power off the computer? The BNC ethernet wire was shocking me with electricity. I grounded it, but how much does leak to ground that way? The grounding sparks a little when disconnected. If I leave the battery charger plugged in, it's warm even if it's not charging any batteries. ...and so on. I switch all the huge energy hogs off, but there are many dozens of small devices which pull 5, 10 watts of energy, 24/7 and it really adds up. A quick and easy way to measure actual power usage of a device would be really nice.

Opposing anectodical evidence:

[imsabbel]

I had about 1-2 bulbs breaking a year.
About 4-5 years ago, i started replacing the broken ones with fluorescent bulbs.

Not a single of those ever died.

Handy Display

[bogamo]

What we really need is a display on the wall, next to the thermostat, that looks like the fuel economy guage on the Prius. On the right is the current consumption, on the left is a bar chart showing past consumption averaged over 5 minute periods. It makes driving the prius like a video game where getting the highest economy is the goal. I'd think if we had such a display, you'd keep track of your consumption, and you'd know if you were drawing more power than you should be for any given time; like leaving a light on in the basement.

How can we expect people to conserve without any easy-to-see meausrement of consumption.

          -Geoff

AMR meter

[dschl]

See if you can get your power company to install an electrical meter with radio-read capabilities. I'm more familiar with water meters, which come in at least two flavours - radio read that sends a signal back in response to a message from the meter reader (using a hand-held meter reading "gun"), and a unit which sends a small packet of meter information every 1-5 minutes. Some info on Wikipedia about automatic meter reading (AMR).

Then all you have to do is possibly reverse engineer their protocol, or at least connect a radio transceiver to your PC and program your own meter reading software.

Of course, I think you are worrying too much about having instantaneous data. I would approach your power usage as an environmental auditing problem. Your power use is more a result of your long term habits and the devices you use. Does it really matter whether your computer and 22" CRT use 600 or 800 watts combined when you know that a Mac mini and LCD would probably use half of that or less? Do you really need to leave your computer on overnight? Does it matter that you have energy saving light bulbs if you leave every light in the house on all day? Is your refrigerator more than 10 years old? Are your appliances energy star rated? Do you hang your clothes to dry outside whenever you can, or do you use an electric clothes dryer?

For power consumption, average long term values are more going to be more important than real-time numbers. By changing your habits and the way you use energy, and tracking the changes and the effects on power consumption as you do that, you'll have more of an impact, that will last far longer than your current fascination with your power usage. You might want to measure the total energy used in a day or a week by various appliances such as your fridge or your TV, in order to determine whether it makes sense to replace them with more energy-efficient models. Beyond that, electrical powered devices use power, just like cars use gasoline. If you choose to use them, you're going to have to pay.

Re:I have a system that periodically updates me

[hotdiggitydawg]

Kill the water heater except immediately before showering.

Or get a power-shower. Or, even better, shower at the gym. I do it because (a) it forces me to stay in the habit of going to the gym every morning, and (b) someone else pays for my hot water. Sure, I pay a gym membership, but I would pay it anyway (at the same price) just to keep fit.

Simple, inefficient solution: save your own energy, use someone else's.

(cheaply!) -- Is free cheap enough?

[bloodSausage]

Depending on where you live, you might be able to borrow an energy meter for free. For example, in Ottawa (Canada), the public library system has about 200 Kill-A-Watt meters available to borrow for three weeks, just like a book (search for "kill-a-watt").

Check out the standby power consumption. I was surprised by my powered subwoofer taking 8 watts when it's "off". Along with the TV (6 watts), receiver (6 watts), and DVD player (4 watts), that was enough waste to make me turn them off at the power strip.

Turn off everything you don't need

[borfast]

This seems pretty obvious but I constantly see people leaving stuff turned on when they're not using it.

Leaving the TV set on when you're not watching, leaving the light on when you're not in the room, leaving the water running while you brush your teeth, you name it, wate of energy and natural resources seems to flow in some people's bloodstream!

And those poor bastards who use that lame-excuse-for-an-instant-messaging-program called MSN Messenger have a special way of wasting energy: leaving their computers on all the time so they can have their nicknames online. Why? Want to receive messages that are sent to you while you're not logged in? Use ICQ. I know the new version of MSN Messenger (or Windows Live Messenger, or whatever) stores messages for you while you're away but ICQ has always done it. Or even better, why not use e-mail, which serves exactly that purpose - sending messages that can be read at a later time?

But I know the culprit

[Coppit]

For my house, A/C is by far the biggest chomper of energy. During the summer months my electric bill gets as high as $270, and during the winter it gets as low as $70. Not only that, but on hot (97 degrees f) days my upstairs never gets cooler than about 78f.

It's a fairly new house, so I can't simply replace the upstairs unit, but I think it's clear that they didn't install a large enough one. What can I do? Put another powered roof ventilator in? Add more insulation in the attic? Put a radiant barrier on the underside of my roof?

This website helps to answer these questions. It provides some analysis of the different scenarios. Dunno if the analysis is accurate or not...

Indirect solution

[Stavr0]

Add up the electrical bills, heating bill, gasoline and battery receipts. You then need a formula to convert monetary unit to energy. This formula should take into account the proportion of each energy form you consume. I think a typical formula will be something around 45% electric, 45% oil/gas and the rest in batteries.

Gasoline produces 32 megajoule/litre, 1 kWh is equivalent to 3.6 megajoule so 1 litre of gas ~= 10kWh. 1 kwH of electricity ranges from 5c to 25c depending where you are.

For Canada:
1 MJ of oil energy ~ $0.04
1 MJ of electric energy ~ $0.03

How much is a MJ of of electric or oil energy where you live?

Re:two cheap AVOs

[zippthorne]

Even if you do understand the above, don't try it. Oh sure, if you want to be nice to the power company, it will provide some useful information, but p(t) = v(t)*i(t) does not mean that P_av = V_av*I_av, or even P_rms = V_rms*I_rms unless voltage happens to be a linear function of current. (or vice versa.) In which case you don't even need to measure both.

If you don't know what you're doing, a real laboratory instrument will be much, much less accurate than an inexpensive device specifically intended as a power analyzer.