How much electricity $ for PC 24x7?

[PlanoMike]

My electical engingeering skills need some help...I'm trying to determine the cost of keeping a PC on 24 x 7, i.e. if I dedicate one to be an HA system, how much is the cost to keep it going?

We'd be taling a low cost machine with 512k to 1G ram, a single hard drive, and integrated graphics. I would leave the monitor off most of the time (in fact, it may not have a monitor...I might just access it via Remote Desktop).

 

[WayneW]

What a coincidence, I just took the Kill-A-Watt power meter off the kitchen PC this morning after gathering data for 20 days. It is a small HP machine with a 17" CRT, but it gives you some numbers and an example to start with.

It draws 104 watts with the monitor on and 37 watts with the monitor off/sleeping. Overall it drew 26.76 kWh over 482 hours for an average of 55.5 watts, which is mostly impacted by monitor usage. I also discovered that the monitor draws about 2 watts when turned off and the PC still draws 8 watts when turned off. So, unplug stuff you won't be using for a while.

So 55.5 watts average times 8766 hours per year produces 486513 watt hours. Divide this by 1000 to get 486.513 kilo watt hours per year. Multiply by $.11 (my average electric rate per kWh) to get $53.51 per year.

So in simple math, it costs about a buck a watt year, so a 150watt power PC would cost $150. Of course, this doesn't account for the heat load on your heating and cooling bills. In Florida, heat is rare, so I get no benefit from the heat and it costs me more for extra AC in the summer. It is probably only pennies, but it can add up with multiple machines.

 

[WayneW]

The hard part is determining the true current draw, for a worst case scenario, you can use the power supply rating of the PC. But I think the PC above had a 150 watt power supply and it normally doesn't draw anywhere near that.

To get an accurate number, use a Kill-A-Watt or a Watts-Up.

http://www.ambientweather.com/tdp4400.html
http://www.smarthome.com/9055.html

 

[kwilcox]

Here in chilly WI, my three server (HCA, Media and Development) system also heats the Office, Sewing room and Library in the winter. These heavily insulated rooms are in the basement. I was amazed by the fact that the extensive individually controlled 240V baseboard system I installed is almost never used. Anyone interested in this little construction project can find it documented here.

 

[lazyone]

Here is a simple spread sheet that calculates the energy cost for any device. Enter your local utility rate in the yellow box. Then, enter your estimated wattages in the W/hr column and the hours per day Hrs/day column. The remainder of the calculations are done by the spreadsheet.

Hope it help.

lz1

*** If using Firefox, you may need to right click and choose "save link as". The default filename will be "index.php". Change the name to "cost.zip" and save the file. Unzip "cost.zip" and all should work.***

 

[opie]

When you think about it that's not a huge amount of power consumption but I think PCs could be more efficient. The New Horizons spacecraft, on its way to Pluto right now, uses approximately 28W while traveling and will peak around 190W when it is gathering data near Pluto. That blew me away when I heard that.

Anyway, I have been wondering the same about the cost of running PCs 24X7 so thanks for starting the thread.

 

[huggy59]

Of course PCs can be more efficient. A laptop uses low-power components and chips, which are more efficient, and also more costly. So the trade-off is cost...

The spacecraft you mentioned isn't a $300 PC...

As for PCs drawing power when off, they aren't off most of hte time these days. They supply a base amount of power for things like wake on LAN, etc. That means the power supply is operating, and since it is a switching power supply, some load must be present for it to work. So it's always drawing power unless it has a separate power switch onthe power supply or you unplug it. Just like most wall-warts and X10 modules... start adding up all that power supply current or the trickle current and it can get your electric bill up there.

 

[miked]

We have a lot of PC's running all the time. The automation/HTPC, the media server PC, a second HTPC in the bedroom, and my work PC (which does various backup tasks every night). There's definitely a bump in my electric bill compared to my neighbors. But not as much a bump as installing electric radiant flooring in the master bathroom!

 

[hgupta1]

I got my kill-a-watt today...very informative!

Although nothing is too expensive to own...all the little things add up. And some of the items that I thought were energy hogs are fairly conservative (like the lcd screen and stereo I use as a TV).

The security PCs and MCE PC with accessories were typically about 180 to 200 watts while running in normal mode. (about 40 watts for the accessories like routers, wall warts, printers, speakers and switches)

The big surprise so far has been my pond pump. 270 watts, 24 hours a day!

I think I am going to put all my spare X10 appliance modules to work so that they cut the power to devices when I won't notice (like when I am at home or asleep).

 

[PlanoMike]

Thanks for everyone's input.

I am thinking about building a PC for HA use, and perhaps as an HTPC also.

Do any of the desktop motherboards (esp. those that could be used in a small form factor "quiet" case) use the more energy efficient laptop-type CPUs...I'm not thinking I need the world's most powerful PC for this?

Alternatively, if one sets up all of the energy saving features on a standard motherboard, do they approximate the same level of low power drain on idle as a laptop typme machine would?

Mike

 

[hgupta1]

There's an article at eHome upgrade about a new Asus motheboard that does use the more energy efficient mobile CPUs. Its pretty much designed for media center.
here

Personally, I don't use any power saving features for my HTPC or my security/home automation PC because the WAF would drop if she had to wait for something to boot up, and I want the home-automation computer to be as responsive as possible.

 

[supie]

Here is a simple spread sheet that calculates the energy cost for any device. Enter your local utility rate in the yellow box. Then, enter your estimated wattages in the W/hr column and the hours per day Hrs/day column. The remainder of the calculations are done by the spreadsheet.

Hope it help.

lz1

Hi Lazyone,

Tried to download your Spread Sheet zip file but it malfuctions and only opens as code?

Could you repost the download link.

Thanks

 

[lazyone]

Here is one way to download the zip file in my post above.

If using Firefox, you may need to right click and choose "save link as". The default filename will be "index.php". Change the name to "cost.zip" and save the file. Unzip "cost.zip" and all should work.

If using IE, just choose "save attachment" and it will save the attachment.

I'm not sure if uploading the file again would fix anything. I believe it is the interaction between the web server code and and the latest firefox.

 

[supie]

Here is one way to download the zip file in my post above.

If using Firefox, you may need to right click and choose "save link as". The default filename will be "index.php". Change the name to "cost.zip" and save the file. Unzip "cost.zip" and all should work.

If using IE, just choose "save attachment" and it will save the attachment.

I'm not sure if uploading the file again would fix anything. I believe it is the interaction between the web server code and and the latest firefox.

This worked thanks.

With IE 6.O right click and select "save attachment as"

 

[Dean Roddey]

Good performance, lower power consuming systems are going to be coming up, from what I've been reading. So I think that this picture will improve a lot in years to come. It looks like Intel/AMD are backing off the pure clock speed route of performance improvement and going back to smarter, less power consumptive, less heat generating schemes I guess.