How Much Power Do You Use?

I'm a bit of a freak when it comes to computers - even some of me geeky friends regard me as an aberration because I have four workstations and two laptops in my house at any given time.  They all serve a purpose, but I won't get into that now, because the point of this post is this: computers use electricity.  The ten thousand dollar question is: how much do they use?

To answer this, I ordered a Kill-A-Watt from Amazon.com.  It's a nifty little device that allows you to easily measure how much electricity any given device uses.  Simply plug the meter into the wall and your device into the meter.  It almost instantly tell you how many watts-per-hour (Watt-Hours, or wH) the item draws.  After that, it's a matter of simple math to figure out what your electricity bill will be.  In my neck of the woods, we pay 10 cents per kilowatt-hour (KwH), so divide your wH by 1000 (to get KwH) and multiply by .10 (the rate charged) to get your cost for using the device.

The Computer
I measured our computer in the den for starters.  It's a Compaq Presario with a 3GHz Intel Celeron chip inside.  Under normal usage, it draws about 101 watts per hour on average (not counting the monitor, printer, or anything else - just the computer).  We probably use it about 3 hours a day - the rest of the day, it goes to standby mode, during which it draws about 2 watts per hour.  Over the course of one day, that means it draws about 345 watts.  Multiply that by 30 (days, in your average month), and I come up with 10,350 watt-hours.  Divide by 1000 to get 10.35 kilowatt-hours.  Now multiply that by 10 cents (0.10), and I find that it costs me $1.04 per month to run that computer (again, not counting the monitor, scanner, printer, or other peripherals).

Now, for those of you paying attention to that last bit, you noticed that the computer was using 2 watts in standby mode.  What happened when I turned it off?  It still drew 1 watt.  That concept of drawing power when turned off came up again and again when I measured more devices.  More on that later.

Monitors
Now, how about the computer monitor?  Well, on the aforementioned Compaq, we have a 19" Philips CRT monitor - you know, the old-school, big, tube-type that takes a lot of space on the desktop.  Under normal usage, it drew anywhere from 66 to 85 watts, depending on what was on screen.  The more white, the greater the power draw, so if you spend more time in Word, or on most web pages, there's going to be a lot of white, hence, more power draw.  In the standby state, I found the CRT was drawing 6 watts.  Taking into account the usage and formulas described above, we arrive at a monthly cost of $1.06 - slightly more than the computer itself.

Contrast that with what I found on my 19" Samsung LCD (alas, it's no longer available unless you want the widescreen) that I use on my main workstation.  It consumed only 25 watts during usage - regardless of what was onscreen.  And under both standby mode and in the off state, it consumed 0 to less than half a watt.  In the same usage scenario as above, that means it costs less than a quarter a month to run.  Tres slick.

The Plot Thickens
Then, I found the pig of the household - the homebuilt Athlon XP 2500 machine that constitutes my main workstation.  There's nothing really outstanding about it - it has the aforemention Athlon chip, 1GB of ram, a measly 64MB GeForce MX440 graphics card, a 90GB and a 20GB hard disk, and a CDROM drive.  This thing pulled 110 watts at idle, and up to nearly 130 watts at full bore.  Standby mode still pulled 62 watts, but it wasn't even configured for that, so it was pulling nearly 110 watts all day long.  A little math showed that it was costing me roughly $7.50 a month.  The bulk of that is due to leaving it on 24/7 and not configuring it to go to sleep.

Miscellany
The other interesting and somewhat annoying discoveries were from the television end of things.  We still have a late-80's era 25" Zenith tube TV that drew a respectable 60 watts during normal usage (contrast to the 19" Philips' 75 watt draw), but drew 10 watts when turned off.  That's just abominable.  Our newly acquired 32" Vizio LCD widescreen pulls about 80 watts during use, but nothing when turned off.  That means we could watch the Viz for 3 hours a day, every day, for a whole year, and it would cost the same as just leaving the Zenith plugged in - without ever turning it on.

The other annoying thing was the DirecTV HD satellite box.  It drew 20 watts all the time - turned on or off.  That equates to about $1.55 a month.  Not that you can do anything about it - unplug it, and you have to go through a 10 minute download every time you plug it back in - or just plain get rid of it.  But from what I've heard, cable TV boxes aren't any better.

So What Is The Moral Of The Story?
Well, I can't exactly tell you that investing in better stuff will save you hundreds of dollars.  I won't make back the $25 cost of the Kill-A-Watt in a month - but I'll likely save close to a hundred dollars over the next year.  You can likely shave a bit off your electric bill by following a couple simple guidelines:

• LCD monitors trump CRTs.  They can draw as little as one-third of the electricity for comparably sized screen.  Added bonus:  you'll get a lot of your deskspace back.
• Either turn your computer off when you're not using it, or make sure it's set up to either sleep or hibernate when not in use.  Newer computers (3 years old or less) have better power management skills.  Older ones - probably not so much.
• Buying a new computer or have a slightly older one that you're wondering if you should hang on to?  Pay attention to what's powering it - specifically, the CPU.  AMD's Athlons and Intel's older Pentium 4's are pigs.  The Intel Core Duo and Core 2 Duo chips are nice and fast, and draw a lot less power.  Apple's new Mac Minis, iMacs, and MacBooks all use them, and they use very little power.