Just bought a Kill-A-Watt electricity consumption meter

[Lazarus]

Just bought a Kill-a-watt for $19.00 including shipping. Couldn't resist.

If you want one try here. Good till 01/13/08

[newtonsfirstlaw]

These things rock. I have the Australian version, which I patiently waited for something like 2 years to finally get here. I've since conducted a thorough energy audit of the whole house. I was surprised that some things don't use as much energy as you think. For example, my CRT only used 60W, and it's 19 inch. Of course, an LCD can use half that, easily.

It pays to measure. If only it weren't so difficult to measure drag coefficient.

[bennelson]

For real fun with the Killawatt, make sure to measure electronics when they are turned "off".

I have heard that up to %75 percent of all the electricity consumer electronics use is when they are "off"

A VCR, Sattelite reciever, cable TV box all use the same amount of power wether they are on or off.

If it has a remote control, clock, or blinking light, unplug it when not in use.

[newtonsfirstlaw]

Originally Posted by bennelson

For real fun with the Killawatt, make sure to measure electronics when they are turned "off".

Absolutely. I think also that the killawatt may not register below about 5W. So if a device uses 4W, it will read 0W. Can Americans confirm?

The way to test this is to plug a powerstrip into the killawatt with a resistive load such as a desk lamp and the device you test into that powerstrip. Measure the difference between your device on and off, with the desk lamp running.

This was the motivation to buy a power strip with individual power switches. Stuff that uses no power when switched off goes on my old power strip, anything that uses power when switched off gets switched off with the switched power strip.

[bennelson]

I have noticed the Killawatt seems to be inaccurate at low wattage.

Does anyone know of another product that would be good for measuring low current AC? Something inexpensive, or better yet, a DIY project for how to make one?

[newtonsfirstlaw]

Originally Posted by bennelson

I have noticed the Killawatt seems to be inaccurate at low wattage.

Does anyone know of another product that would be good for measuring low current AC? Something inexpensive, or better yet, a DIY project for how to make one?

Well, seeing as most people use the Kill-a-Watt about once, which is when they audit their house and write down figures for on and turned off, it's easy to just use the Kill-a-Watt.

The trick (not sure if I made it clear) is to measure what you want to measure in parallel with another, bigger, purely resistive load. The difference (with the resistive load on, and the smaller device in question on/off) will be the power draw of the smaller device. Yes, I know that taking power factor into consideration, it won't be exactly correct but it will be close enough.

[roflwaffle]

Originally Posted by newtonsfirstlaw

Absolutely. I think also that the killawatt may not register below about 5W. So if a device uses 4W, it will read 0W. Can Americans confirm?

Mine measures down to 2W IIRC. I don't think I've measured any 1W devices, and the 2-3W was an old microwave.

[trebuchet03]

Originally Posted by newtonsfirstlaw

Absolutely. I think also that the killawatt may not register below about 5W. So if a device uses 4W, it will read 0W. Can Americans confirm?

I got pretty close to accurate readings at 2W testing a strand of LED lights confirmed with multimeter... I haven't really verified things less than that...

I've been doing long term power usage measurements with my kill-a-watt

things like my cell phone charger, laptop charger, etc. The wattage reads as zero (occasionally hitting 1) - but given enough time, it will show up in the kWh reading...

My laptop charger, for example, consumes ~.15kWh per week... I had a spare power brick on the kill-a-watt for three weeks.... Which almost makes me sad because that's less than 8kWh per year if the charger was on stand by the while time... That costs me about 75 cents, a year... It's not like I can go to people with a huge claim of how much they'll save - I find more than 75 cent/year on the street

My cell phone charger is almost half that consumption...

[Who]

Anyone have two kill-o-watts so they can find out how much a kill-o-watt uses?

I have the WattsUp Pro that graphs and found it invaluable for doing run time optimization with a new boiler installed last winter. You could tell when it was idle (14 watts for the controller), when the pump was active (70 watts more), and when it was ignited, the approximate fan speeds all by fixed time intervals (20 to 50 watts more depending on modulation).

I was tempted to get a newer one that had more data storage (as it uses up each time interval range, it basically just uses every other data point and then records on the newly liberated second half so it can go on and on and on with wider and wider data acquisition intervals, although data was quite good over 24 hour periods) to smoothen out graphing and make it more precise for longer runs. I held off... Then I was tempted by it being USB instead of serial as those ports slowly disappear. The latest is web-server functionality so you can monitor it online. I think that last feature might be the real wallet-spreader. It's coming in February, so I'll have to remind SWMBO I have one of those gift-receiving occasions that month!

https://www.doubleed.com/secure/products.php

[SVOboy]

I'm pretty sure the kill-a-watt monitors lower than 5 watts, but I don't remember getting the impression it was overly accurate.