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Measuring the Energy You Use?

Cliff posted more than 7 years ago | from the how-many-kilowatts-do-you-burn-in-an-hour dept.


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?

cancel ×


Stating the obvious (5, Insightful)

iainl (136759) | more than 7 years ago | (#16111965)

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.

Re:Stating the obvious (-1, Offtopic)

Anonymous Coward | more than 7 years ago | (#16111995)

Holy shmoly, I have a huge boner!

Weird units (2, Funny)

QuantumFTL (197300) | more than 7 years ago | (#16111968)

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 (5, Funny)

Anonymous Coward | more than 7 years ago | (#16112065)

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

Re:Weird units (1)

mangu (126918) | more than 7 years ago | (#16112255)

I thought you measure energy in ounceyards or something like that?

Watt/kilowatt hours are a kind of convenience measurement, they are not international system units. Like kilometers per hour, those units simplify day-to-day use, but make things more complicated for calculations.

The real source of the problem is that there has never been an accepted day-to-day system of decimal multiples for the second, which is the SI unit of time. Ultimately, this would be a difficult thing to implement, given that human life is dependent on sunlight and seasons. The earth's rotation around its axis and around the sun aren't exact multiples, and they vary from day to day and from year to year. That's why there are leap days and leap seconds.

The second, which is the *only* unit of time in the international system, has a precise and well defined value. This value is obtained from measurable physical properties, such as the frequency of vibrations of atoms under well-defined circumstances. For scientific and many engineering uses, one needs to use such precise values.

OTOH, for many other uses one doesn't need all that precision, even the most fussy person wakes up in the morning at a time whose accuracy will never be better than a second or so. Farmers need to know the season of the year within a day or a week, they don't go like "...OK, summer starts at my count, 3, 2, 1, NOW!".

That's why there are two different measurement systems for time, one is the precisely defined second, in which calculations never employ such fuzzy units as hours or days or weeks, and the other system uses the messy sexagesimal multiples system that comes all the way from ancient Babylon. To help bridge the gap between both systems people sometimes use hybrid measurement units such as "kilowatt-hours" or "kilometers-per-hour".

The use of minutes with sixty seconds and days with twenty four hours may seem as awkward as feet with twelve inches or pounds with sixteen ounces, but it's a different situation. We cannot measure days and seasons with exact decimal multiples because the duration of days and seasons is variable and they are not locked in step. A day is 86400 seconds long. We could declare a new unit of time, such that a day would be exactly 100000 new-seconds, for instance, but what would be the use? The next day would last a little bit longer, because the earth's rotation is slowing down due to the energy lost to tides. A year is approximately 365.25 days, and this length varies from year to year. Some years are a little bit shorter, some are a little bit longer, depending on the exact pull the other planets exert on the earth's orbit.

That's the reason why we keep the ancient system, changing it would be inconvenient without any appreciable benefit. But there is no rational reason for keeping other ancient units for measuring lengths, weights, volumes, or temperatures. Most of the world has accepted this simple fact and adopted more practical units for these measurements.

Re:Weird units (1)

lord sibn (649162) | more than 7 years ago | (#16112344)

No, we use rods, and we measure them by hog's head.

Re:Weird units (1)

Waffle Iron (339739) | more than 7 years ago | (#16112530)

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

No, silly. That unit doesn't make any sense because it doesn't define units of energy. You probaby mean ouncedalyards. That's what I use; it's the perfect unit for my job of designing elevator systems for chipmunks. It's just a trivial conversion:

$ units
2438 units, 71 prefixes, 32 nonlinear units

You have: ouncedal*yard
You want: watt*hour
* 2.1947974e-06
/ 455622.92

Re:Weird units (0)

Anonymous Coward | more than 7 years ago | (#16113784)

I believe Murphy's Law requires that we express everything in furlongs per fortnight.

Re:Weird units (0)

MrNaz (730548) | more than 7 years ago | (#16112121)

It blinks at 1 watt-hour?

Over how long?

I'm getting sick of people confusing watts and watt-hours.

Someone write up a once-and-for-all explanation for all the idiots here who have no idea watt the difference is.

Re:Weird units (1)

xutopia (469129) | more than 7 years ago | (#16112144)

Why don't you get off your high horse and write it up?

Re:Weird units (1)

Lars Clausen (1208) | more than 7 years ago | (#16112153)

Well, go back to bed then. The powermeters measure your usage in watt-hours, not watts. So an LED that blinks when a watt-hour has been used is meaningful (if less useful than, say, a digital read-out of watt-hours used). Thus if it blibnks once per hour, you are using one watt-hour per hour, or one watt (on average during that hour).

Re:Weird units (2, Informative)

Schraegstrichpunkt (931443) | more than 7 years ago | (#16112402)

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

Re:Weird units (0)

Anonymous Coward | more than 7 years ago | (#16112552)

I'm getting sick of people confusing watts and watt-hours.

I take it there are no mirrors in your house.

Re:Weird units (1)

MindStalker (22827) | more than 7 years ago | (#16112755)

No, it couldn't blink at 1 watt. 1 watt is a measure of speed of flow. If you want to measure an amount of electricity you use watt-hour which means the amount of energy used in an hour with a 1 watt flow. Obviously if you were using say 60 watts, you would be using 60 watts in an hour, OR 1 watt hour every minute.
So it would blink once a minute.

Re:Weird units (4, Funny)

Keebler71 (520908) | more than 7 years ago | (#16112443)

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!"

Re:Weird units (0)

Anonymous Coward | more than 7 years ago | (#16112941)

That's really poor mileage you know. 40 (rod / hogshead) = 0.00198 miles per gallon [] or 10 1/2 feet per gallon. Everything grandpa needs is within ~100 feet of the fuel depot?

I have a system that periodically updates me (1, Insightful)

BadAnalogyGuy (945258) | more than 7 years ago | (#16111969)

I use a periodic system to update me of my power usage. It comes in the form of a letter from the power company and it tells me how much power I've used as well as the cost for usage for that month. It's really convenient, but I am not really interested in the dirty details of where all that usage is going.

I suppose if you're really interested, you could try turning off your A/C or electric heating. Kill the water heater except immediately before showering. Turn off lights you're not using. Turn off any computers that are unessential. And CLOSE THE GODDAMNED DOOR. WE'RE NOT COOLING THE WHOLE OUTSIDE!

Re:I have a system that periodically updates me (1)

kfg (145172) | more than 7 years ago | (#16112008)


Damned straight, so long as the device is running we're heating it.


Re:I have a system that periodically updates me (2, Funny)

Anonymous Coward | more than 7 years ago | (#16112066)

Turn off any computers that are unessential.
But this is slashdot, where unfortunately uptime is more important than power saving.

Re:I have a system that periodically updates me (2, Interesting)

hotdiggitydawg (881316) | more than 7 years ago | (#16112418)

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.

For an individual device (4, Informative)

keithmo (453716) | more than 7 years ago | (#16111975)

Re:For an individual device (3, Informative)

djmurdoch (306849) | more than 7 years ago | (#16112028)

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 (4, Informative)

subreality (157447) | more than 7 years ago | (#16112043)

That's why we have the Watts Up Pro: [] . 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 (0)

Anonymous Coward | more than 7 years ago | (#16112484)

but the best thing about it: it measures and displays the True power of Richard M. Stallman

Re:For an individual device (1)

JoeCoder7 (989774) | more than 7 years ago | (#16113120)

This one [] is qite a bit cheaper at $30.

Re:For an individual device (1)

Temkin (112574) | more than 7 years ago | (#16112158)

I have one. The parent's comments are right on target. Despite these little annoyances, it is quite handy. I found mine retail at Camping World of all places.

Re:For an individual device (2, Interesting)

ObjetDart (700355) | more than 7 years ago | (#16112689)

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.

Re:For an individual device (1)

xmas2003 (739875) | more than 7 years ago | (#16113063)

Ditto what others said - yea, the Kill-A-Watt ain't perfect, but cheap and works as advertised. Note that it has some time history capabilities too as long as it is left plugged in. One interesting thing to do is hook it inline on your PC and watch the power draw change between "idle" and when it's "full on"

I've also used it to measure current draw on my christmas lights [] to make sure I don't exceed 15 Amps on a circuit - I try to stay under 10 by load balancing.

Re:For an individual device (1)

szembek (948327) | more than 7 years ago | (#16112455)

This is the only response needed to this askslashdot article. Maybe the submitter should try google next time.

Re:For an individual device (1)

ealfert (551051) | more than 7 years ago | (#16113642)

Kill-A-Watt monitors electric usage for 1 device or one powerstrip. $30 []

The Energy Detective (TED) monitors the entire house. $140 []

I have both of the above. I use Kill-A-Watt for easy analysis of a device and TED for monitoring the turning on/off of major appliances. I also switch the wiring of TED to my generator to monitor it and make sure I don't go over desired load.

Watt's Up Pro is like Kill-A-Watt is for 1 device or one powerstrip but has additional features similar to TED. $120 []

Re:For an individual device (1)

jnik (1733) | more than 7 years ago | (#16113782)

Does it actually work with computers? I've been told that switching power supplies can confuse the cheaper Wh meters.

Datacentre (4, Informative)

IckySplat (218140) | more than 7 years ago | (#16111980)

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 nergy_Devices.html?gclid=CJ2il5S3r4cCFTpsEAod3n1L- Q [] 3,1324,1328&mid=4084 []

Enjoy :)

Conserve it anyway first (2, Insightful)

arun_s (877518) | more than 7 years ago | (#16111983)

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 (2, Informative)

Anonymous Coward | more than 7 years ago | (#16112118)

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.

cheaply measure a single device (1)

way2trivial (601132) | more than 7 years ago | (#16111994)

Re:cheaply measure a single device (4, Informative)

Myself (57572) | more than 7 years ago | (#16112061)

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:cheaply measure a single device (1)

Jaseoldboss (650728) | more than 7 years ago | (#16112392)

For the whole house you need a current clamp meter [] with a remote display.

Don't know if they have one for US voltages though.

Re:cheaply measure a single device (1)

Skynyrd (25155) | more than 7 years ago | (#16113017)

For the whole house you need a current clamp meter with a remote display.

Don't know if they have one for US voltages though.

It may be a good product, but their advertising is horrible. Yes, I hate flash.
They claim it "can save up to 25%" on your electric bill. That's simply a lie. It can show you how much power you use, but it can't save power. I never deal with liars like this - kind of like spammers.

Take a look at this: []
Same idea, and a good multimeter as well.

Re:cheaply measure a single device (1)

Jaseoldboss (650728) | more than 7 years ago | (#16114115)

The site is terrible but I like the idea.

Two things wrong with them at the moment IMHO: too expensive and no history display.

I built something to do that (0)

Anonymous Coward | more than 7 years ago | (#16111998)

Homebrew is the way, particularly if you are interested in electronics. I have a similar meter - this is what I did:

Get a photo-diode, and make it face the blinking watt-hour LED. Use a comparator to convert the state of the LED to a logic signal. Then connect that logic signal to your computer. I did this by having the signal trigger an oscillator which sends an audio signal to my computer's sound card when the LED is on. There are other ways to sample an external signal (e.g. parallel port) but this was the easiest way to arrange things. A program on the computer is constantly listening to the line input: it counts the interval between pulses and calculates the power consumption from that.

Re:I built something to do that (1)

kfg (145172) | more than 7 years ago | (#16112099)

There are other ways to sample an external signal (e.g. parallel port)

Yep, the photo sensor can be pluged into the parallel port to trigger the internal counting circuit of the cpu. Don't even need to make up a plug, just put pins on the leads and plug them directly into the appropriate holes in the socket. You can run up to eight counters at a time this way (but at that point you'll want to build a cable).

If you're using a USB printer this may be the way to go, since the only thing you have to "build" are the wires onto the photo sensor. The logic circuit is already built in to your computer.

As an aside you can make your own computer controled breakbeam devices this way too. Just put an infrared emiting diode on one side , a sensor plugged into the parallel port on the other and when the beam is broken it triggers the internal counter. Now just write the software for whatever you want to happen at a trigger event. Silent alarm, not so silent prerecorded greeting, turn a light on or off, etc.


Easily enough (0)

Anonymous Coward | more than 7 years ago | (#16112025)

My exercise bike automatically displays the energy that I use. I usually quote it in megajoules since it sounds more impressive that way.

well, (4, Informative)

joe 155 (937621) | more than 7 years ago | (#16112036)

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, (1)

BadAnalogyGuy (945258) | more than 7 years ago | (#16112045)

I find that the failure rate of energy efficient fluorescent bulbs is about the same as normal incandescent bulbs, so any cost reductions on the power bill get negated by the high cost of replacement.

Stick with normal bulbs. The cost/benefit ratio is no worse than energy efficient bulbs and you don't have to suffer through the "warmup" period that fluorescent bulbs typically have right after you turn them on.

Re:well, (2, Interesting)

joe 155 (937621) | more than 7 years ago | (#16112076)

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, (1)

SharpFang (651121) | more than 7 years ago | (#16112142)

The hourly rating in their case is completely meaningless number calculated basing on some average based on expected usage.

Normal fluorescent lamps lifetime professionally is not rated in hours but in switch-on operations. Leave it on for a month, you might have decreased its lifetime by 0.01%. Toggle the switch 500 times in 1 hour, you decreased the lifetime by 10%. Bulbs are way more resistant to this problem, but switching them on does shorten their life too.

Another factor is working conditions. Primarily power supply - I found the energy-saving lamps to die within a week of usage on a line with "dirty" power - voltage at about 90% of norm, lots of spikes, noise etc. Same brand works for years in conditions of good power in places where they are switched on once and left running, never switched off, in temperature never dropping below zero and low humidity. In both cases the numbers are nowhere near what was written on the box, but if you'd average the numbers you might likely get somewhere near the stated life expectancy.

Re:well, (2, Interesting)

rhandir (762788) | more than 7 years ago | (#16113911)

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.

Opposing anectodical evidence: (2, Interesting)

imsabbel (611519) | more than 7 years ago | (#16112089)

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.

Re:well, (0)

Anonymous Coward | more than 7 years ago | (#16112141)

Try another brand. Cheap compact fluorescents are crap. They don't last long enough and they emit "low quality" light: Their spectrum is uneven because they typically contain only two phosphors. The result is bad color reproduction. Often surfaces which are white under natural light appear to have a greenish undertone under these cheap fluorescents.

Also make sure you get the right color temperature. Lightbulbs emit 2700K light. That is "warm" light and a good choice for living areas. Compact fluorescents with that color temperatures are available. Office areas should use higher color temperatures.

A good way to sell people on compact fluorescents is to make the light brighter than before: Don't replace 60W bulbs with 60W-equivalent compact fluorescents. Use a 100W equivalent CF. They still use only about 20W, so you save about 1kWh per week if you replace a bulb that is on for 4 hours each day. At 15ct/kWh, the CF has saved $12 after 2000 hours (500 days at 4 hours per day), which is much less than they are guaranteed to last, so you can expect even bigger savings, all the while enjoying light which is 50% brighter.

Re:well, (1)

plover (150551) | more than 7 years ago | (#16112315)

I find that the failure rate of energy efficient fluorescent bulbs is about the same as normal incandescent bulbs

Ouch! Fortunately, I haven't had the same bad luck as you.

About three years ago I started switching over to compact fluorescent (CF) bulbs as my tungsten bulbs have died. The ones I've bought have a 7 year guarantee (cheapos from Home Depot.) I've taken to writing the install date on them with a sharpie marker before putting them in the fixtures. Yes, I know I'll never find the original receipt so the warranty is most likely useless, but I'm curious to see if they do last as long as advertised.

So far, I haven't replaced any failed CFs. I particularily like having them in the sealed ceiling fixtures as they don't generate nearly the heat of the tungsten bulbs they replace. Yes, I know the fixtures are designed with heat insulation to protect against fire, but 26W simply emits much less heat than 120W. I feel safer.

Re:well, (1)

subreality (157447) | more than 7 years ago | (#16112058)

You're making the measurement more complicated than it has to be. Light bulbs and ovens list how much power they use.

Re:well, (2, Interesting)

sbryant (93075) | more than 7 years ago | (#16112114)

... 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, (1)

joe 155 (937621) | more than 7 years ago | (#16112151)

Ah, you remind me of a very good point which I forgot to mention, If you have a TV on stand-by it can use almost as much power as if it is on (at least they used to - and probably still do). I was amazed at just how much power things can use in stand-by. It really is worth switching things off properly, as you say, at the plug if neccesary.

The small hastle of losing the clock on a TV and having to walk over to do it is nothing when thinking about the energy you'll save

Re:well, (1)

jrmcferren (935335) | more than 7 years ago | (#16112263)

Not anymore, the old TVs you are talking about use tubes. The new ones are solid state and do not keep heater current flowing to the CRT (which is why they still have to warm up). You are talking about 4-10 Watts Max even for a HUGE CRT projection or plasma set. Standby modes have come a long way. Light bulbs, however is where the majority of the energy waste is at. I would go into more detail, but that would be redundant and I have to get my ass to class.

Re:well, (0)

MindStalker (22827) | more than 7 years ago | (#16112634)

I always thought would be an interesting idea would be to connect every light switch in the house to a motion sensor. If you turn off the light it stays off, but if you turn it on it goes off once you leave the room. Any idea how many watts those small motion sensors use?

Replacing Appliances Usually Not Worth It (1)

dmatos (232892) | more than 7 years ago | (#16112947)

If you do a cost-benefits analysis on replacing appliances with more energy-efficient models, you'll find that it's usually not worth it, unless the old appliance is already at the end of their life.

Say you have a fridge that cost $800 to buy, and you've had it for 10 years. If you think it will last another 10 years (not unlikely), then by throwing it out now, you're throwing out $400 worth of value (using a gross simplification). How many kWh would you have to save over the next 10 years to add up to that $400? And if you're looking at just the energy consumption of the device, from a purely environmental standpoint, throwing out a fridge only halfway through its life is throwing away half of the energy used in its production. This is not an inconsequential amount.

While I heartily agree with replacing dead appliances with more energy-efficient ones, I do recommend some deeper analysis before any functioning ones are thrown out to make room for newer things.

Re:Replacing Appliances Usually Not Worth It (1)

TheOtherChimeraTwin (697085) | more than 7 years ago | (#16113002)

The Refrigerator Retirement Savings Calculator [] answers just that question. That old refrigerator some people keep for extra space can be pretty expensive.

Re:Replacing Appliances Usually Not Worth It (1)

Suidae (162977) | more than 7 years ago | (#16113461)

If you do a cost-benefits analysis on replacing appliances with more energy-efficient models, you'll find that it's usually not worth it, unless the old appliance is already at the end of their life.

The benefit part of the analysis is not always simply savings on your electric bill. If you live off-grid or have a whole-house backup power system the reduced energy consumption of a highly efficent appliance reduces the cost of your power storage/generation requirements or extends your backup times.

You can also consider the environmental benefit in the analysis. Saving power reduces the rate of resource consumption (but usually not at a rate that justifies replacing a working appliance! It costs energy to make the new one, so environmentally speaking you may be wasting resources by taking a working appliance out of service. You can always give/sell it to someone else who needs it though).

Insane measuring (2, Informative)

Jboost (960475) | more than 7 years ago | (#16112057)

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.

Easily said. (2, Insightful)

SharpFang (651121) | more than 7 years ago | (#16112074)

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.

Re:Easily said. (1)

Temkin (112574) | more than 7 years ago | (#16112201)

I always hated thinnet's little electrical fangs. Remember to only ground one end.

If I might ask... Why are you still running it?

Re:Easily said. (1)

SharpFang (651121) | more than 7 years ago | (#16112423)

'cause the dogs broke the only piece of twisted pair long enough to reach to mom's bedroom to network her computer. Plus all the ports of the switch are already occupied by my own hardware, only the BNC connector is available. Her computer is too weak to make any use of 100mbit or wifi anyway and I'm not quite in mood to buy extra hardware.

Re:Easily said. (1, Interesting)

Anonymous Coward | more than 7 years ago | (#16112348)

Buy a power strip with an in-built on-off switch. We have the kind with a lamp inside the switch that glows when it's on.

Connect all your computer equipment to the strip (routers, monitors, computers), and turn it off when you don't use it. Do the same for the TV & stereo.
  Your equipment won't use any energy if the power isn't connected...

When you go to bed, you notice if the lights are shining or not. If they are, turn them off. Presto!

Re:Easily said. (1, Interesting)

Anonymous Coward | more than 7 years ago | (#16112364)

Stand by mode is a killer. We all have lots of devices on standby and they each use power. I'm surprised your monitor is using a massive 40W, turn that bugger off when you don't need it, please! An example, the TV, STB and DVD were using 20W when all on stand by. Seeing as these things are not used most of the time, that's a lot of power wasted over a year just from one socket. Now we physically kill the power.

One problem we have in the US is the power sockets do not have switches, and no one likes to pull the plug many times as it invariable weakens the socket. Other counties have switches, so it's a lot easier. The beefy UK ones are great.

Go to amazon and look at the "kill a watt" devices. They'll tell you the juice your using from a given socket.

Watt Meter for European Sockets? (1)

RAMMS+EIN (578166) | more than 7 years ago | (#16112077)

Now that this is on topic, let me ask:

Where can I buy an inexpensive Watt meter for use with European sockets? Preferably in the Netherlands, but any place that will ship to the Netherlands is fine, too.

Re:Watt Meter for European Sockets? (1)

imsabbel (611519) | more than 7 years ago | (#16112097)

Any electronic retailer has them for like 5EUR.
(i know that reichelt, ELV and conrad catalogues have them listed)

1/1000 of a KWh? (0)

Anonymous Coward | more than 7 years ago | (#16112130)

That was known as a watt/hour for about a billion nanocenturies!

Reminds me of old jokes about everyday distances measured in attoparsecs and the like, some were really funny. Anyone got some links?

Re:1/1000 of a KWh? (1)

Schraegstrichpunkt (931443) | more than 7 years ago | (#16112447)

Anyone got some links?

You could probably find some on Google [] .

Even for RC planes (1)

Pegasus (13291) | more than 7 years ago | (#16112131)

For electric powered, of course. There's a nice little device called Watt's Up that you hook between your motor controller and battery and displays about everything you need to know to optimize your setup. I did a short review [] , becaue I plan to create a competition based on how little energy you spend on your model flying. Should be interesting, fun and educational.

Re:Even for RC planes (1)

The_Mr_Flibble (738358) | more than 7 years ago | (#16112293)

I would like to enter my bomber, however is it based on mass and size of model or just flight time/power usage ? It runs on 4 speed 600 motors and I run a 8.4v 3300 mah nihm on it. I can get it airborn and fly round the field once. On the plus side I can launch my other smaller planes from it.

two cheap AVOs (1, Informative)

ajs318 (655362) | more than 7 years ago | (#16112132)

Get two cheap AVO-knockoffs, one of which must have an AC current range. Measure the voltage across the appliance and the current flowing through it. (Note; you will inevitably be measuring either the current drawn by the voltmeter or the voltage drop due to the ammeter. Neither matters much with modern instruments.) Multiply the current by the voltage to get the power in watts, divide by 1000 to get kW, and multiply this by the time in hours to get Units. (1 Unit == 1 kWh == 3.6MJ). For geek points, interface all this lot to a computer. Since you'll be dealing with mains, your circuit will need to be optically isolated. I recommend to build the whole measuring circuit "live", and use an ADC with a synchronous serial output. This way you only need clock and MUX drive (voltage / current selection) in, and data out; you can use just one dual and one single opto-isolator on the printer port. If you don't understand the above, don't try it.

I have also seen standalone plug-in power analysers with a pass-through socket and an LCD showing, in turn as you press a button, the voltage, frequency, current, power, time and energy consumption. They aren't as accurate as a real laboratory instrument, but you get what you pay for.

Re:two cheap AVOs (2, Informative)

zippthorne (748122) | more than 7 years ago | (#16113229)

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.

I use a "Watt's Up" (1)

bbaxem (1002967) | more than 7 years ago | (#16112178)

1800 watt (~15 amp) maximum; LCD display; ampere, watt & power-factor modes; built-in tracking totals; possible PC integration: []

Meter Actual (2, Informative)

techpawn (969834) | more than 7 years ago | (#16112199)

A lot of times energy companys just make an estimation of that you bill SHOULD be. If it seems unually high you can request them to come and get an actual reading on your meter. If you're meter still reads high then you should start checking the things that the others have posted about. Not only may this identify that there IS a problem but could also save you some coin on the bill. At least that's how it works in the private sector.

My UPS has a report (1)

plover (150551) | more than 7 years ago | (#16112265)

My UPS (an APC Back-UPS RS 1500) came with their "PowerChute" utility. The "Current status" screen has a 'Load on battery backup' indicator that tells me I'm drawing 268 Watts of power through the UPS right this instant. (That means I'd burn 268 Watt-hours if the computer were to remain in this state for one hour.)

Of course, a 50 pound battery isn't very portable, and I wouldn't drag it around to the refrigerator, dishwasher, lamp, or garage. But I'm mostly interested in the computer's draw anyway, since it's one of the biggest power drains in my house.

Re:My UPS has a report (1)

The_Mr_Flibble (738358) | more than 7 years ago | (#16112305)

however your ups is adding another 100w to that total just keeping it powered. Try plugging in a watt meter in front of the ups and have a nice shock at the amount ofpower you really use on your computer.

usage (0)

Anonymous Coward | more than 7 years ago | (#16112332)

Turning off your lights and computers really won't do that much. ~50% of one's home energy usage is for HVAC. About 20% tends to be for hot water. If your fridge is more than say 15 years old, it probably accounts for another 10% of usage. Lights are usually ~10%, and computers, electronics etc are usually less than 10% of one's usage.

Handy Display (4, Interesting)

bogamo (96489) | more than 7 years ago | (#16112356)

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.


Re:Handy Display (0)

Anonymous Coward | more than 7 years ago | (#16112993)

"What we really need is a display on the wall, next to the thermostat, that looks like the fuel economy guage on the Prius."

That is a great idea.

I would buy one.

How quickly can you bring it to market?

Maybe as a kit, with a portable KillAWatt to measure individual devices too.

Re:Handy Display (0)

Anonymous Coward | more than 7 years ago | (#16113006)

A very similar device is manufactured by Blue Line Innovations [] in Canada

It uses a device attached to the electrical meter on the outside of the house, which transmits the current consumption information to a display inside, which will show how much you're currently using and how much you've used since the unit was last reset. The present model works on electromechanical meters (basicly counts the revolutions of the wheel with the black mark on it), but a new one will be available very soon (any day now ...) which will also work on digital meters (with the 1 watt hour pulses).

Hydro One in Ontario, Canada has a program to distribute up to 30,000 of these devices in Northern Ontario. Pilot studies have shown that consumers will cut back their usage by 10-15% when they have this kind of real time information in front of them.

Possibilities (1)

gweihir (88907) | more than 7 years ago | (#16112388)

To measure cheaply on a single devices, get a used mechanical power meter.

For automation, it getst expensive. Basically you need a power meter with some sort of interface. I expect this to be in the $300 plus price class, since it is professional equipment and not mass-market.

AMR meter (2, Insightful)

dschl (57168) | more than 7 years ago | (#16112404)

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.

(cheaply!) -- Is free cheap enough? (5, Interesting)

bloodSausage (98859) | more than 7 years ago | (#16112466)

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 (2, Insightful)

borfast (752138) | more than 7 years ago | (#16112515)

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 (4, Informative)

Coppit (2441) | more than 7 years ago | (#16112556)

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...

Re:But I know the culprit (1)

localman (111171) | more than 7 years ago | (#16113340)

That sure does seem high. I live in Las Vegas and my 2100 sqft house comes in at $170/month in the summer and as low as $30 in the winter. Are your windows and doors sealed properly? Maybe there's some missing stripping? Not sure if it would help in your case, but solar screens [] can help. I don't even have them, though. But a lot of people around here do.

Good luck.

Same here. (1)

antdude (79039) | more than 7 years ago | (#16114059)

My room can go up to 90F degrees in the hot days. Central unit doesn't work. I heard having those mini-AC for the room works. However, I have no room for it and I am worried about its power usage for the room (can cause power breakages?).

Power Angel (0)

Anonymous Coward | more than 7 years ago | (#16112664)

Seasonic makes a device called the power angel ( [] ). You plug a device into it and it measures the power that it's consuming, and a few other quantities. I've found it to be very useful.

Centameter (1)

nathanh (1214) | more than 7 years ago | (#16112672)

I use a Centameter [] . The measuring device is installed in the meter box. You carry around a wireless LCD display that shows power usage in either kWh or A. I managed to reduce my house standby power usage from 0.44kWh to 0.21kWh because I discovered some appliances with atrocious standby usage; they're now turned off when not in use. That's going to save me $282 per year - I pay 14c/kWh - so the meter has paid for itself already.

Indirect solution (2, Interesting)

Stavr0 (35032) | more than 7 years ago | (#16112859)

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?

Kill-A-Watt (1)

NekoXP (67564) | more than 7 years ago | (#16112923) []

Search for Kill-A-Watt.

It will track the consumption of a device (or even a breakout block with 4 sockets, with this thing in the wall) over a period of time.

The alternative is replace the power distribution box in your house so you can monitor each room's usage.

A step further (1)

John Napkintosh (140126) | more than 7 years ago | (#16112925)

Lots of devices, even when turned off, draw power in a standby state. The only way to find out which ones do that and how much they draw is to use a killawatt or something similar.

I'm pretty anal about energy conservation. I have nearly all of my powered devices plugged into strips. I frequently not only turn off the device when I'm done using it, but also the strip itself when I know I'm not using any of the devices on the strip. This prevents slow current usage by devices even in their standby state. Any devices that aren't able to maintain their settings when the lose power (and don't have some form of built in battery back-up, like my alarm clock) get plugged directly in to the wall.

Why it is probably pointless (1)

texaport (600120) | more than 7 years ago | (#16113173)

1st scenario: Use more energy this winter and the greenhouse gas effect rises;
with the subsequent warmer weather, less energy use will follow.

2nd scenario: Use less energy this winter and the greenhouse gas effect drops;
with the subsequent colder weather, more energy use will follow.

The bulb that changed the world... (1)

murphotronic (985577) | more than 7 years ago | (#16113263)

recent slashdot link: bulbs.html [] I knew they were more efficient, but the numbers are pretty staggering. CFL's are the next wave... until LED's become cost effective for mojor lighting tasks

Monitoring Power Usage (0)

Anonymous Coward | more than 7 years ago | (#16113287)

Here is a site that has made me excited about monitoring the power usage in my home: []

Clap on... (1)

Chapium (550445) | more than 7 years ago | (#16113478)

This might help: The Clapper []

Results of detailed measurements (0)

Anonymous Coward | more than 7 years ago | (#16113820)

I clipped AC current sensors onto my house's main lines, and used an old serial-port A/D converter to sample twice a second for a couple weeks. You can tell a lot just from the gross current draw, because most of the big power users have recognizable fingerprints: refrigerators have startup transients, the microwave oven has no startup transient and a precise duty cycle, the electric range (at 220V) draws from both sides simultaneously, et cetera.
Details at tMeasure/index.html [] .

Energy YOU use? (Vague story title) (0, Offtopic)

awtbfb (586638) | more than 7 years ago | (#16113828)

My first thought was that you wanted to measure how much energy your body used [] . Ooops.

Cut Power Factor to cut your bill? (0)

Anonymous Coward | more than 7 years ago | (#16113877)

(just kidding) All you have to do is hook up a large induction motor right after your meter. Then connect that shaft to a dynamo rated for the max consumption of your house, plus a safety factor - for a typical US house a 7500W generator should do fine. You still get to use all the energy you were using before, but with a power factor of about 0.2, they bill you a LOT less! (/just kidding)

But really - has anyone noticed that 'they' are phasing out low-watt appliances in favor of higher consumtion ones: 15 years ago I had a 900W hair dryer. When that died, I couldn't find anything under 1200W. When -that- one died last year, I couldn't find anything less than 1850W. Seems just like the W98 -> W2K -> XP expandable bloatware effect.
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