I recently purchased a Kill-A-Watt electric meter, which is a device you can use to measure how much energy an electrical appliance is using. I used my kill-a-watt around both my and my parent's house (my Dad was really interested too), and took some readings. Some were surprising, others were not. It's worth noting that large appliances (TVs, refrigerators, computers) often have a spike in power usage immediately when they are turned on, but usage quickly drops once the startup time has passed. I have tried to note the startup spike where I can, but it is brief and it can be hard to get a reading.

I found it interesting that on a CRT TV screen, the power usage changes depending on what is on the screen. For example, an image with a lot of bright white uses more power than a dark image. For a rear projection, LCD, or plasma TV, this situation is probably different.

We tested my parent's refrigerator for an hour to measure how many kilowatt-hours (kWh) it used. Because it cycles on and off, this gives a better understanding of it's usage over time. Over 60 minutes, keeping the door closed the whole time, the compressor cycled on and off twice, and overall it used 0.08 kWh.

I've decided to keep monetary cost out of the equation, because the real cost of energy goes way beyond how much you pay your electric company each month.

Here's a table of my readings. I'll be adding more as I take them. If you have an idea for something you'd like measured, let me know!

Kill-A-Watt Readings
Device State Watts
40W incandescent bulb on 40
Torch-style halogen lamp on 266
LED night light on 0
20" CRT TV w/ built-in VCR off 3-5
20" CRT TV w/ built-in VCR on 50-70
32" CRT TV off 5
32" CRT TV on 65
32" CRT Sony Wega TV off 1
32" CRT Sony Wega TV startup 89-262
32" CRT Sony Wega TV black screen 86
32" CRT Sony Wega TV blue screen 103
32" CRT Sony Wega TV green screen 99
32" CRT Sony Wega TV red screen 120
32" CRT Sony Wega TV white screen 130
Panasonic 42" Plasma Standby 19
Panasonic 42" Plasma Startup 133
Panasonic 42" Plasma Picture 100-151
Panasonic 42" Plasma Black 60
Panasonic 42" Plasma Blue 265
Panasonic 42" Plasma Cyan 342
Panasonic 42" Plasma Green 252
Panasonic 42" Plasma Magenta 350
Panasonic 42" Plasma Red 210
Panasonic 42" Plasma White 360
Panasonic 42" Plasma Yellow 330
Stereo head unit off 1
Stereo head unit startup 52
Stereo head unit idle 34-36
Stereo head unit playing music 36-40
Powered sub-woofer idle 7
Powered sub-woofer playing music 7-11
Digital cable box (no DVR) standby 13
Digital cable box (no DVR) on 13
Refrigerator fan only 23
Refrigerator compressor startup 225
Refrigerator compressor running 190
TiVo (Series 2 standalone unit) startup 40
TiVo (Series 2 standalone unit) on 28
Linksys WRT54G (Wireless/ cable router) off 1
Linksys WRT54G (Wireless/ cable router) on 4
Motorola cable modem on 4
Computer speakers (stereo + subwoofer) muted 1 2-3
Computer speakers (stereo + subwoofer) idle 2 6
Computer speakers (stereo + subwoofer) in use 6-10
Dell Inspiron 4150 laptop off 3
Dell Inspiron 4150 laptop standby 2
Dell Inspiron 4150 laptop hibernate 3
Dell Inspiron 4150 laptop startup 40-50
Dell Inspiron 4150 laptop idle 28-30
Dell Inspiron 4150 laptop high CPU usage 49-55
Dell Inspiron 4150 laptop LCD power save 18-20
Dell Inspiron 4150 laptop (linux) startup 30-47
Dell Inspiron 4150 laptop (linux) idle 28-29
Dell Inspiron 4150 laptop (linux) high CPU 49-55
Dell Inspiron 4150 laptop (linux) LCD power save 20
Dell Inspiron 8600 laptop off 0
Dell Inspiron 8600 laptop on 20-33
Shuttle SN25P Computer hard off 3 0
Shuttle SN25P Computer soft off 3 9-12
Shuttle SN25P Computer startup 126-155
Shuttle SN25P Computer idle 2 83-84
Shuttle SN25P Computer file copy (disk to disk) 87-89
Shuttle SN25P Computer video card demo 160-180
Shuttle SN25P Computer high CPU load 144-155
Cell phone charger charging 1
Bluetooth headset charger charging 1
Alarm clock on 1
Carbon Monoxide Detector on 0-1
Philips LED Rope Light on 1
Dell 2001FP 20" LCD Monitor Off 0
Dell 2001FP 20" LCD Monitor Standby 4
Dell 2001FP 20" LCD Monitor On 48
HP dv9000t laptop idle 35
HP dv9000t laptop heavy disk use 40
HP dv9000t laptop dvd burning 42
HP dv9000t laptop off 1
HP dv9000t laptop startup 55
HP dv9000t laptop arithmetic test 55
HP dv9000t laptop multicore efficiency 57
HP dv9000t laptop multimedia test 63
1 The speakers don't have an "off" button, only a "mute" button.
2 idle: on but not doing anything significant.
3 Most computers these days are not really "off" when you turn them off. They draw power all the time for various reasons. "Hard off" is where I turned off the main power supply switch on the back of the machine. "Soft off" is where the rear switch is in the "on" position, but the computer itself is not "on".

Specs on the Shuttle SN25P are:

  • Athlon x2 (Dual Core) 4200+
  • 2GB RAM
  • ATI Radeon X800XL Video Card
  • 250GB SATA Hard drive