high on solder

Recently I purchased a Kill-a-watt power meter and since then I have been testing the power usage of my various PCs. The Kill-a-watt is a low cost ($20) wall outlet power meter that will display the voltage, amperage, frequency, power-factor, wattage, volt-amps and kilowatt-hour usage of whatever you have plugged into the unit. In order to do a well rounded test of my computers I decided to monitor the power used during various activities. I tried to do tests that best matched tasks I primarily use the machines for (laptop for productivity, desktop for gaming, etc). I was most interested in testing my HTPC since it is turned on almost 100% of the time, so I left it plugged into the Kill-a-watt for 4 days to get a good average usage sample. The tests I decided to run were the following:

Off - phantom power usage when unit is turned off
Standby - power draw when in standby mode
Typical - usage during general computing and web browsing
Video Playback (SD) - power usage while watching a standard definition video
Video Playback (HD) - power usage while watching a high definition video
FLAC to MP3 Conversion - a real world test intended to load the CPU but not the GPU
Gaming (Mafia) - test performed in Windows to give a reference for an older game
Gaming (Half-Life 2) - test performed in Windows to give a reference for a newer game

Here are the specs and power test results for my laptop, desktop, and HTPC.

Dell M1330 Laptop

• Intel T7250 Core 2 Duo CPU (2.0 GHz, 65nm)
• nVidia 8400m GS GPU
• LED backlit LCD display
• 65W power supply
• OS - Ubuntu 8.04 Linux & Windows XP SP2

• Off - 0W
• Standby - 0W
• Idle - 23W
• Typical - 27W
• Video Playback (SD) - 30W
• Video Playback (HD) - 36W
• FLAC to MP3 Conversion - 45W
• Gaming (Mafia) - 54W
• Gaming (Half-Life 2) - 56W

Desktop

• AMD Athlon 64 X2 3800+ CPU (2.0GHz, 90nm)
• nVidia 7900GS GPU
• 500W Antec Earthwatts power supply
• OS - Windows XP SP2

• Off - 2W
• Idle - 99W
• Typical - 105W
• Gaming (Mafia) - 130W
• Gaming (Half-Life 2) - 158W

HTPC

• AMD Athlon 64 3200+ CPU (2.0 GHz, 90nm)
• nVidia 7600GS GPU
• 250W Shuttle power supply
• OS - Mythbuntu 8.04 Linux

• Idle - 67W
• Video Playback (SD) - 69W
• Video Playback (HD) - 80W
• FLAC to MP3 Conversion - 96W
• 4 Day Average - 67.5W

Going into these tests I knew that the laptop would draw the least power, but after looking at the data I have come to a few interesting conclusions:

1. Percentage wise the jump in power usage between the two gaming examples on the laptop vs the desktop are very different. This is most likely due to the considerably more capable Core 2 Duo CPU in the laptop not having to do nearly as much work as the Athlon 64 X2 in the desktop. Also the much more powerful GPU in the desktop has extra settings turned on (such as anti-aliasing) that are not used on the laptop.
2. As in #1 the laptop doesn't have to work much harder to play HD video than SD video, while the HTPC must do considerably more work to achieve the same performance.
3. I was pleasantly surprised to see how efficient my HTPC is. Recently I had been considering upgrading to a newer more efficient processor and motherboard, but after this test I don't feel I would be saving too much power. As you can see from my 4 day average test, the system runs at idle almost all the time. 67.5W per hour spread over a month is 48.6KWH. According to my last electric bill I pay $0.0455 per KWH, therefore the cost to run my HTPC for the month comes to only $2.21. Even with a new machine twice as efficient I would only be saving about $12 a year. This savings hardly offsets the hundreds I'd have to invest in a new system when my existing HTPC still performs adequately.

These tests were a lot of fun to do and I plan on doing more on the rest of my electronics in the near future.