Leaving a Computer On

[The Master of Tarquin Hill]

What would be the price difference on a utility bill between running a computer for a couple hours a day or leaving it on all the time?

Of course, different people are going to pay different amounts depending upon where they live.

I am interested in this because I'm wondering if participating in SETI@home would have a significant impact on my bill.

 

[Robert Maxwell]

Depends... what kind of computer is it?

A quick calculation shows a typical PC, left on for 24 hours a day, year-round, would cost you in the neighborhood of $200-300 a year in electric bills. This is if you're in the US, mind you. I don't remember if you are.

 

[Amaris]

I have an iMac Core Duo 17" and an HP Small form which both use about 110-115 watts each. Calculating their wattages at maximum, I would pay, on average, $13 a month to keep both of them on 24/7. In actuality, that number is closer to $8 a month for both because I implement energy solutions on both, but they do stay on all year round.

J.

 

[AdmiralGarak]

Depends... what kind of computer is it?

A quick calculation shows a typical PC, left on for 24 hours a day, year-round, would cost you in the neighborhood of $200-300 a year in electric bills. This is if you're in the US, mind you. I don't remember if you are.

Do those calculations take into account stand-by mode and turning off monitors? CRT monitors, especially, are big power guzzlers.

 

[Marc]

Depends... what kind of computer is it?

A quick calculation shows a typical PC, left on for 24 hours a day, year-round, would cost you in the neighborhood of $200-300 a year in electric bills. This is if you're in the US, mind you. I don't remember if you are.

Do those calculations take into account stand-by mode and turning off monitors? CRT monitors, especially, are big power guzzlers.

CRTs use only a little more power on a per square inch of real estate than the LCDs (came up in an earlier thread in here) so a 19" LCD is going to use almost as much power as a 19" CRT.

Other factors can include the CPU, the amount of memory, video card.

 

[The Master of Tarquin Hill]

Depends... what kind of computer is it?

A quick calculation shows a typical PC, left on for 24 hours a day, year-round, would cost you in the neighborhood of $200-300 a year in electric bills. This is if you're in the US, mind you. I don't remember if you are.

Do those calculations take into account stand-by mode and turning off monitors? CRT monitors, especially, are big power guzzlers.

CRTs use only a little more power on a per square inch of real estate than the LCDs (came up in an earlier thread in here) so a 19" LCD is going to use almost as much power as a 19" CRT.

Other factors can include the CPU, the amount of memory, video card.

Celeron

 

[Jadzia]

Computers all use different amounts of power.

Modern cpus alone can be anything from 20W to 120W when working 100%.

But for a rough estimate:

In 24 hours, expect 2 kWh if it is running idle with no monitor (ie, low power mode). But expect around 3-6 kWh per day if it is with monitor and working above idle. (ie, full power mode)


You might be better off running this project from a laptop. If you already have one, then that would be about 1/4 of the power.

Or buy a netbook, because it uses negligible power, and it will pay for itself in a couple of years in the savings you make from 24/7 electricity costs.

 

[Robert Maxwell]

Ice Queen's suggestion is good.

And I didn't take standby mode into account because the OP said it would be left on all the time for SETI@Home.

$200 is what a "typical" computer plus CRT would cost at 11 cents per kWh, averaging 240 watts of constant usage.

 

[Deks]

If you leave the computer on for long periods of time, but in idle mode and with a screen off, the energy expenditure will be quite small actually.

But let's face facts, there is little to no point leaving a computer active for days if you have no intention in using it for that amount of time.

I have both desktop and a laptop.
Unless I expect to do some work on my desktop, I keep it off, while I keep the laptop on at virtually all times (because I use it for all my work).
If I have nothing large to download during the night ... then I keep the laptop off as well (or put it to sleep) and turn it on again in the morning ... but it wouldn't really matter since it's power requirements are much lower compared to the desktop while retaining a lot of the cpu/gpu power.

Of course that no power expenditure is more desirable than the opposite ... but the differences are not that big actually.
Unless our power requirements increase exponentially, I don't see the big effect on the power bill.

 

[Mr. Laser Beam]

Aren't most computers which use *nix variants (Linux, OS X, etc.) actually *meant* to be left on all the time? I know that OSX's cron jobs can only be done when the computer is on and awake.

 

[Jadzia]

If you leave the computer on for long periods of time, but in idle mode and with a screen off, the energy expenditure will be quite small actually.

But let's face facts, there is little to no point leaving a computer active for days if you have no intention in using it for that amount of time.

I thought that processors have power stepping modes, where "idle" or "low power mode" is where it is using less than about 2% cpu, and it automatically switches its clock down to 200MHz clock and uses a fraction of the power, or something like that.

I don't know how much cpu power this project would take, whether it would run in idle or not.

 

[Santaman]

^^ Nope, no OS except maybe those on mainframe computers need to run 24/7/365 and even then I assume that in the case of mainframes its more a hardware thing then a software thing to leave the machine running.

 

[Robert Maxwell]

A system running an intensive program like SETI@home would rarely go into low power or idle CPU mode. So there wouldn't really be a power savings there. The CRT being off would help, though.

On the question of whether a PC should be left on all the time: it used to be true that it was generally bad for a PC to be shut off, because the "cold start" of turning it on really stressed the components. However, that stopped being a problem with the advent of ATX power systems, which have been standard for at least the last 8-10 years. An ATX system uses a microswitch rather than a hard switch, and so the system is always receiving a small trickle of power, even when the computer is "off." This prevents cold starts and reduces component stress. Thus, it is not necessary to leave the computer on all the time, because in a sense, it is on all the time.

 

[Deks]

Nevertheless, computers rank low on power usage regardless on how you look at it.

Besides, they were designed to run 24/7 without shutting down or resetting (so were the OS-es).

Most newer cpu's have the ability to downclock in idle mode and as a result use much less power than usual.
This is hardwired into the Core Duo, Core2Duo, Quad etc. techs ...
So yes, the power requirements (especially in idle mode) will be barely noticeable when it comes to the bills.

But as I also previously stated ... if you won't be using your computer for a certain period of time, then there's no point in keeping it active.
I just shut it down if I don't use it at all for a day or more.
If I have a background program though that I want operational, then I just leave that, set the screen to turn off after a few minutes, and that's it.

 

[Marc]

A system running an intensive program like SETI@home would rarely go into low power or idle CPU mode. So there wouldn't really be a power savings there. The CRT being off would help, though.

haven't looked at seti@home for a while but iirc loads the data into memory and then chews away so you could spin down the hard disks when running over night.

 

[Captain Intrepid]

Ice Queen's suggestion is good.

And I didn't take standby mode into account because the OP said it would be left on all the time for SETI@Home.

$200 is what a "typical" computer plus CRT would cost at 11 cents per kWh, averaging 240 watts of constant usage.

Shit, 11 cents per kWh? Expensive electricity! Thats almost twice what I pay.

 

[Jadzia]

Think yourself lucky your not in England, it's 11p per kWh here. Convert that into your green dollars.

 

[Captain Intrepid]

Think yourself lucky your not in England, it's 11p per kWh here. Convert that into your green dollars.

Multicoloured actually! I live in the good old Dominion of Canada.

 

[Pingfah]

I used to leave mine on all day, its a pretty standard PC, I guess it must be a guzzler because I started saving quite a significant amount of money (english money) when I began turning it off when i'm not using it.

 

[Capt. Vulcan]

Running it on a laptop would save on your electricity bill, but then wouldn't the trade off be that you'd end up doing less processing for the Seti project?