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Measuring the Energy You Use?184

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?
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Measuring the Energy You Use?

• Stating the obvious (Score:5, Insightful)

on Friday September 15, 2006 @06:22AM (#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.
• Weird units (Score:3, Funny)

on Friday September 15, 2006 @06:23AM (#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 (Score:5, Funny)

by Anonymous Coward on Friday September 15, 2006 @07:00AM (#16112065)
You have Wh in the US? I thought you measure energy in ounceyards or something like that?
• Re: (Score:2)

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

• Re: (Score:2)

We'd change to a decimal system for the same reason we changed the other units: it's simpler to do the math.

One day is 10000 seconds, 100 minutes, 10 hours. How long is your TV show? A deca. Or half-deca after commercials. How long's it take to run a marathon (if you're worth your salt)? An hour. Fly from LA to NYC? 2.5 hours, or 2 hours and 50 minutes. Time to run the 100 meter dash? 1.04 seconds. A snap of the fingers? millisecond.

But yes, all for naught if you can't find a natural way to calibr
• Re: (Score:2)

The problem with using base 10 math for stuff like that is that it doesn't divide evenly. How often do you convert units when talking about time? A fair bit if you're a researcher maybe, but for most people it's not very often at all. On the other hand, how often do you have to split segements of time in half, thirds, quarters, fifths, or even sixths? Quite a bit if you're like most people. Using 60s, 12s, and 24s a lot (perfect numbers) makes that problem easy. You almost never get messy decimals unl
• Re: (Score:2)

Remember boys and girls, 1 watt-hour is 14160 yard-ounces!
• Re:Weird units (Score:5, Funny)

on Friday September 15, 2006 @08:40AM (#16112443) Journal
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: (Score:2)

Note to Mods: this isn't flamebate. I heart Canada. Please send me all of your magnetic money.
• For an individual device (Score:4, Informative)

on Friday September 15, 2006 @06:26AM (#16111975) Homepage
• Re:For an individual device (Score:4, Informative)

on Friday September 15, 2006 @06:45AM (#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 (Score:5, Informative)

on Friday September 15, 2006 @06:52AM (#16112043)
That's why we have the Watts Up Pro: http://www.thinkgeek.com/gadgets/electronic/7acf/ [thinkgeek.com] . 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: (Score:2)

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: (Score:3, Interesting)

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 viciou
• Re: (Score:2)

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 [komar.org] to make sure I don't exceed 15 Amps on a circuit - I try to stay under 10 by load balancing.
• Re: (Score:2)

My kill-a-watt has two 6' extension cords attached to it I never disconnect. When I want to measure a device, I unplug it, insert that loop, and I'm done. 6' is plenty of cord in most situations to allow you to move the meter to a comfortable reading position, while not being so much that I worry about adding significantly to the power draw. Unless your device is actually in the dark, there is no need for a flashlight, contorting to read the meter, any of that stuff.

That leaves the only real drawback at
• Re: (Score:2)

That's a good solution. I didn't mean to imply that I disliked the device, just that a few of the design decisions that went into it were pretty dumb.
• Re: (Score:2)

This is the only response needed to this askslashdot article. Maybe the submitter should try google next time.
• Re: (Score:2)

Does it actually work with computers? I've been told that switching power supplies can confuse the cheaper Wh meters.
• Re: (Score:2)

I've used the Kill-a-Watt device and blogged about the energy usage of objects in my household - as the article says, it's fairly interesting to be able to gather detailed data like that. http://digitalcrusader.ca/archives/2006/08/househo ld_power_1.html [digitalcrusader.ca]
• Datacentre (Score:4, Informative)

on Friday September 15, 2006 @06:27AM (#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
http://www.energyoptimizersdirect.co.uk/acatalog/E nergy_Devices.html?gclid=CJ2il5S3r4cCFTpsEAod3n1L- Q [energyopti...rect.co.uk]
http://www.blackbox.com/Catalog/Detail.aspx?cid=18 3,1324,1328&mid=4084 [blackbox.com]

Enjoy :)
• Conserve it anyway first (Score:2, Insightful)

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: (Score:2, Informative)

by 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 dryin
• Re: (Score:2)

To be fair, things like computers and light bulbs are less efficent at heating the house than a heat pump, especially a modern heat pump. Anything that is just converting the energy to heat directly (every appliance in your house) does it at a rate of 1 energy unit consumed per 1 unit of heating. A heat pump can move upwards of 3 to 4 units of heat per every 1 unit of energy.

• Re:cheaply measure a single device (Score:5, Informative)

on Friday September 15, 2006 @06:58AM (#16112061) Journal
I love my kill-a-watt [p3international.com] but I've been thinking of picking up a Watt's Up? [doubleed.com] 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 [google.com] 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: (Score:2)

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

Don't know if they have one for US voltages though.
• Re: (Score:2)

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: http://www.tequipment.net/Ideal61-701.asp [tequipment.net]
Same idea, and a good multimeter as well.
• Re: (Score:2)

The site is terrible but I like the idea.

Two things wrong with them at the moment IMHO: too expensive and no history display.
• Re: (Score:2)

It doesn't matter, if it's a current meter, it measures current not voltage; even if it was a power meter, the 220v (I think) voltage in Britain is a bit more than the NA's 124Vrms/220Vrms system so it wouldn't actualy hurt the thing but may cause any wattage measurements to be off by half, if it uses powerline freq for timing, it'll be off by 6/5. If you really want to get technical we can argue over the differences between wattHour and Volt-Ampere-Hours and mathematics involved with Root Mean Square measu
• Re: (Score:2)

I know it measures current but it reports kWh for which it needs to know the voltage.

In any case I can clear this up since I had a quick look through the online manual. It turns out that you specify the voltage in the setup so you can use it in the US. The default currency is even dollars! Unfortunately, they're going to be about \$150 to import so I doubt they get many US orders.

...we can argue over the differences between wattHour and Volt-Ampere-Hours
If you know about power factors you will know that
• well, (Score:5, Informative)

on Friday September 15, 2006 @06:48AM (#16112036) Journal
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: (Score:2)

You're making the measurement more complicated than it has to be. Light bulbs and ovens list how much power they use.
• Re: (Score:2)

With a measuring device you can learn things such as:

How much does my fridge use/day at setting X? setting X-5?
How much does my oven use to cook dinner? Microwave?
How much power does my rig use playing MULE for an hour? Idling?

You can learn a lot. Listed power is only predictable for trivial devices that are always on, not devices with variable load or duty cycles.
• Re: (Score:3, Interesting)

... 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

• Re: (Score:2)

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: (Score:2)

I do the powerstrip thing. In fact, I have one powerstrip that's always connected, and in that powerstrip I have a remote-controlled power-thing, to which I plug additional powerstrips. Whenever I leave anywhere, I simply press off on the remote and my monitor, all speakers, any non-essential devices and chargers/power bricks are out of power, while leaving essential devices on (computers). Same thing when I go to sleep, unless I really need to charge something during the night, and don't feel like jumbling
• Replacing Appliances Usually Not Worth It (Score:2)

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 th
• Re: (Score:2)

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 als
• Re: (Score:2)

If you bought a fridge 10 years ago it is unlikely it will last another 5 years let alone 10.

If you bought a fridge 25 years ago it is highly likely it will last another 15 years.

My washer and dryer are over 25 years old. I'll probably get 40 years service from them. My old fridge has a pink steel shell in it and has to date to the 60's. I'll probably get another 25 years from it. But the last fridge I bought which is in the kitchen has broken 3 times in the last 4 years.

Modern appliances suk.
• Insane measuring (Score:2, Informative)

Take a look at this [bwired.nl] and see how he did it [bwired.nl].

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 su

• Easily said. (Score:3, Insightful)

on Friday September 15, 2006 @07:03AM (#16112074) Homepage Journal
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: (Score:2)

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: (Score:2)

'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: (Score:2)

If you're getting shocked from the shield of your Ethernet wire, you've got problems other than unnecessary electrical use. Something's wired badly, and you've might have an electrocution waiting to happen. Grounding the leakage current is fixing the symptom, not the problem. Fix that first, THEN worry about usage.

If the 22" CRT really uses 40W in standby, put it on a switched outlet. If your computer documentation doesn't say whether USB gets standby power, measure it with a meter. Unplug your battery
• Watt Meter for European Sockets? (Score:2)

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: (Score:2)

Any electronic retailer has them for like 5EUR.
(i know that reichelt, ELV and conrad catalogues have them listed)
• Even for RC planes (Score:2)

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 [f5j.eu], becaue I plan to create a competition based on how little energy you spend on your model flying. Should be interesting, fun and educational.
• two cheap AVOs (Score:2, Informative)

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,
• Re: (Score:3, Informative)

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
• My UPS has a report (Score:2)

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, sin

• Handy Display (Score:4, Interesting)

on Friday September 15, 2006 @08:17AM (#16112356) Homepage
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
• Re: (Score:2)

Actually, I was thinking it might work better with a small Bluetooth device without a display. You plug but and it will send data to your computer/PDA/phone so you can examine the power consumption at all enabled outlets on a significantly larger and more convenient (and more controllable) interface. It would allow easy data aggregation and comparison. The device could even have a memory for storing a few hours or days of data, so you won't have to leave a computer on to monitor it.

It's low power, compact,
• Possibilities (Score:2)

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 (Score:3, Insightful)

on Friday September 15, 2006 @08:29AM (#16112404) Homepage

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 [wikipedia.org] (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? (Score:5, Interesting)

on Friday September 15, 2006 @08:43AM (#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 (Score:2, Insightful)

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 comp [borfast.com]

• But I know the culprit (Score:5, Informative)

on Friday September 15, 2006 @08:54AM (#16112556) Homepage

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 [ornl.gov] helps to answer these questions. It provides some analysis of the different scenarios. Dunno if the analysis is accurate or not...

• Re: (Score:2)

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 [lasvegassolarscreens.com] can help. I don't even have them, though. But a lot of people around here do.

Good luck.
• Same here. (Score:2)

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?).
• Re: (Score:2)

Unless your insulation sucks, if the unit is undersized, all you really can do is replace it. I bit the bullet last year and replaced my 2 ton unit (on a 5 year old house) with a 3 ton, and now it actually turns off in the summer. Still uses just as much power (maybe even slightly more), but at least it cools the place so it is comfortable to sleep.
• Re: (Score:2)

1. Spend some time reading up here: HVAC Talk forums [hvac-talk.com] . A bunch of professionals post here. Number one recommendation for a tricky problem? Get a Manual J inspection by an engineer. Tell the Sales guy at any HVAC contractor that that's what you want. They'll bring a laptop, take measurements, etc. The whole process takes a few hours but will give you a good estimate of actual HVAC needs.
2. For you, I'd recommend moving the thermostat upstairs and having more insulation blown in before considering a larger unit.
• Re: (Score:2)

The way people treat energy usage, you'd think that there's never been an energy crisis.

One thing people can do is to put their other resources to work for them. Most people can't afford to retrofit a geothermal heat pump underneath their house, but there's other options!

Do you have a pool??? Think about how AC units work: they remove heat from inside of the house, and move it outside into the atmosphere. Air, being an excellent insulator, is probably the worst medium to discharge excess heat efficientl
• Centameter (Score:2)

I use a Centameter [centameter.com.au]. 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 (Score:3, Interesting)

on Friday September 15, 2006 @09:35AM (#16112859) Homepage Journal
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.

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: (Score:2)

Ok,

2 x 1000w HPS lights == 720 KwH ~ \$0.06 == \$43.20 per month X 3 months == \$129.60

That would be 2Kg of MJ for \$129.60 :>

• Kill-A-Watt (Score:2)

http://www.thinkgeek.com/ [thinkgeek.com]

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.
• For the true geek who needs to know his power usag (Score:2)

I too wanted to get a handle on my power usage. I found this site that details how to build a complete power meter and interface it to your computer. Let the slashdot effect begin.

http://www.edcheung.com/automa/power.htm [edcheung.com]
• I read about a great solution some time ago (Score:2)

I read about a great solution some time ago, but I couldn't remember where. It might have been here, it might have been digg. Regardless, I found the link with the google query "power monitoring system"

http://www.kondra.com/circuit/circuit.html [kondra.com]

It's very involved and detailed and it looks like anyone who tried to replicate the system would have to spend quite a bit of money, but then you'd have access to all of the data you could ever want about your power consumption.

I'll include the last page of the linked
• network enabled meters (Score:2)

is there a cheap network enabled (snmp) meter? maybe that can help us by allowing us to pool the power consumption with historical charts so we can track our usage. being able to check on the watts usaged at any given moment is good and by turning on/off devices, we can measure its actual consumption (especially the standby and typical ones.)
• Umm buy a meter? (Score:2)

Buy a cheap amp meter and learn how to use it?

Or even better yet how about that thing on the side of your house that has the little shiny spinning disk.. Its not from mars, it tells you total energy useage for your place, both in real time and elapsed.. Its how you get billed each month. Its called a watt-meter, go figure.

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