# Kill A Watt EZ energy meter



## lotuseclat79 (Sep 12, 2003)

Has anyone here bought one of these meters? Looks like a good idea to monitor the consumption of the energy your electric devices while not turned on, and while in use as well. Does Lowe's or Home Depot sell them?

You'll have to google for them to see what price they are going for - found one at $19.99 and another at $29.95 and also at somewhere just above $50.

Read about the device in a NY Times article, Putting Energy Hogs in the Home on a Strict Low-Power Diet, here.

The Department of Energy estimates that in the average home, 40 percent of all electricity used to power home electronics is consumed while the products are turned off. Add that all up, and it equals the annual output of 17 power plants, the government says.

-- Tom


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## kiwiguy (Aug 17, 2003)

I consult occasionally in this area. The profile of domestic power use has changed radically in the last 20 years.

In history, when appliances were "off", there was little or no load drawn, so "low load" periods were almost "no load" periods.

Appliances were relatively inefficient, so "high load" periods were quite high.

Now its all changed, as most appliances are in "standby" instead of "off", and consume a small but still material amount of power. It's all to do with people getting impatient and wanting instant response from appliances and appliances being fitted with electronic clocks which lose their settings when turned off.

On the other hand, many new appliances tend to be more efficient in use now, so peak loads have not increased to any material degree and may have decreased.

But the usage in terms of monthly kWh grows mainly due to the background standby load. If you can identify all such load and turn it off, savings can be made.

In NZ we have this device available, you program it to $ per hour and it gives an instantaneous and 10 second updated cost of the whole house load.
http://www.centameter.co.nz/

I recommend their use to get an understanding of what uses the power in a house.


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## JohnWill (Oct 19, 2002)

This device measures the whole house power consumption, which isn't always the information you want. I like the Kill-A-Watt device because you can measure the draw from a single appliance or device. I see they say that they say:


> The CENTAMETER is sensitive enough to register the savings made by switching off a single 25-watt light.


This seems to indicate that you can't really tell the difference between the "standby" of a typical LCD panel and power off, for instance. My LCD screens consume 2-3 watts in standby...

Of course, the price of this device will put a few people off too.


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## kiwiguy (Aug 17, 2003)

I also have an in-line monitor that I built from a kit, it will record a cumulative load and display it as load in watt-hours or in $.

As it uses a commercial metering chip it will measure down to about 10 mA of load current (2 or 3 watts at 230 volts)

The kit cost was similar to the Centameter (which incidentally is only $130 NZ trade, or $US90)


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## JohnWill (Oct 19, 2002)

I bought the Kill-A-Watt for $20, and it's been handy a time or two. I'm not sure I'd get much use out of one that measured my whole house.

Of course, I have 400A service and three heat pumps to heat/cool a 5000sq/ft house, and there is a LOT of electrical equipment here. Finding 25 watts wouldn't do much for me, I need something to cut big chunks of usage out.


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## kiwiguy (Aug 17, 2003)

400 amps?

Must be that woossy 110v supply that you use over there...

You need a real mains supply, 230v (or 415v 3 phase) that we have as standard here.

Some supplies are now running at 3 phase 690 volts, where submersible deep well irrigation pumps are used that are 200 metres straight down.


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## hewee (Oct 26, 2001)

Where you get Kill-A-Watt for $20 at?


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## kiwiguy (Aug 17, 2003)

http://www.resellerratings.com/forum/showthread.php?threadid=127772


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## JohnWill (Oct 19, 2002)

kiwiguy said:


> 400 amps?
> 
> Must be that woossy 110v supply that you use over there...
> 
> ...


Actually, my incoming power is 400A of 240 VAC. There is a neutral line that comes from the center-tap on the transformer to deliver the 120 VAC to each leg of 240 VAC feed.


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## JohnWill (Oct 19, 2002)

hewee said:


> Where you get Kill-A-Watt for $20 at?


It was a sale that showed up on one of the bargain sites I regularly visit.  It was shipped free as well.


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## kiwiguy (Aug 17, 2003)

JohnWill said:


> Actually, my incoming power is 400A of 240 VAC. There is a neutral line that comes from the center-tap on the transformer to deliver the 120 VAC to each leg of 240 VAC feed.


I am seriously pleased not to have to pay your electric bill!

We have dual secondary single phase supplies here, most small or rural distribution transformers can supply 240-N-240 (or 480 v), but 480v equipment rarely (if ever) exists, so the transformers are strapped to parallel the windings and double the current.

I would find (after 40+ years) that 120 volt cabling would be too bulky, as the currents are too high.

Common GP outlets here are wired in 2.5mm cross section copper stranded (old imperial 7/.029). Good for about 25 amps with close protection, or a 5.8 kW load per circuit. Common domestic network connections are 60 amp rated.


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## hewee (Oct 26, 2001)

JohnWill said:


> It was a sale that showed up on one of the bargain sites I regularly visit.  It was shipped free as well.


Ok thanks


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## JohnWill (Oct 19, 2002)

kiwiguy said:


> I am seriously pleased not to have to pay your electric bill!


Sure, but I don't have any other heating bills, since it's an all-electric house. 


> We have dual secondary single phase supplies here, most small or rural distribution transformers can supply 240-N-240 (or 480 v), but 480v equipment rarely (if ever) exists, so the transformers are strapped to parallel the windings and double the current.
> 
> I would find (after 40+ years) that 120 volt cabling would be too bulky, as the currents are too high.


Standard 110V wiring is #14 wire for 15A circuits and #12 wiring for 20A circuits. One issue of 220V wiring to outlets it the lethality is significantly higher, and we have enough people electrocuting themselves here already! 


> Common GP outlets here are wired in 2.5mm cross section copper stranded (old imperial 7/.029). Good for about 25 amps with close protection, or a 5.8 kW load per circuit. Common domestic network connections are 60 amp rated.


We have many 220V connections for large appliances, but there's really no need to supply a table lamp with a 5.8kw circuit. 

I'm surprised that they use stranded wire, all the stationary wiring in the US is normally solid wire. Stranded is only used for extensions from the wall outlet to the device in question in the US.


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## hewee (Oct 26, 2001)

See How do I find out how much electricity something uses?


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## kiwiguy (Aug 17, 2003)

Stranded wire is used for all but lighting circits which are solid.
But it's not a fine strand, only a 7 core strand.
Our industry is highly regulated, but DIY is OK if an electrician signs off on the compliance.

And we have almost no fatalities on 230v, either trade or DIY persons.

Most fatalities are on 11,000, 33,000, 66,000, 220,000 or 500,000 distribution or transmission lines, due to errors in work practices. Not much left to bury...


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## JohnWill (Oct 19, 2002)

The fatalities with 230V is usually the end users, not the people wiring the circuits. 

It's interesting that you use stranded wire. For really heavy wire, below about #8, I believe it becomes stranded, simply because you couldn't handle larger gauge solid wire easily. I know that the #2 wire coming to my 100A sub-panel here is stranded, as well as the #0000 that feeds the main panel. The cable feeding the heat pumps is also stranded. Interestingly enough, these are all aluminum cable, while the solid cable is copper.


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## kiwiguy (Aug 17, 2003)

My comments on fatalaties also refer to end users. I get to see reports on all or most fatalities and there just are so very few. Last one was a couple of years ago (sure we only have 4 million people...) that I was involved with.

Perhaps as it is 230v they give it more respect? Also the degree of regulation means very few DIY issues and all new houses have compulsory Residual Current Devices (GFI's)

Plus we have an MEN system, all outlets are grounded.


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## JohnWill (Oct 19, 2002)

We don't have GFI's here in the US on all circuits, just outside outlets, bathrooms, and kitchens close to the sink. Current regulations are for grounded outlets, but there are lots of old houses with sub-standard wiring around. I have a friend that still has working knob-n-tube wiring in parts of his house!


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## kiwiguy (Aug 17, 2003)

We never had knob-n-tube here.
The earliest wiring was steel conduit with VIR cables, these are still inherently safe unless disturbed.
Then we went to "Wood casing" around the wartime when steel was in short supply, with VIR in a wood capping enclosure. Again this was fine unless the conductors were disturbed, as the old VIR gets very brittle.

Then we went to TRS (Tough Rubber Sheath) and some early batches of that had crumbling insulation in later years, other batches were fine (my country house has this wiring, it's as good as the day it was installed).

Then we went to the present TPS cabling and Neutral Screened cabling.

While I can DIY as I am fully qualified and registered, the average homeowner seldom does. Until about 10 years ago it was illegal to sell cable or fittings to anyone other than a registered person. Now every hardware store has them, thogh it has not had any negative effect of lives it seems.

The last local death I had any info on was a case of a roofing nail penetrating a TPS cable near a light, livening the roof iron. Was like it for many years and only discovered when the young visitor to the house was using the play equipment that was moved near the house, climbed up and steadied himself on the end of the roof iron. The room light just happened to be on and the roof was alive.

Even at 110v, the outcome may well have been the same, bare feet, bare metal and a good path to ground. The house was too old to have had GFI protection mandated.


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## x31forest (Jul 13, 2007)

If anyone has a Kill-A-Watt handy and some free time, I'd like some help populating my site http://www.thewattdb.com with different devices power draw in standby and active states.

Thanks,
-Paul


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