Energy saving tip – How much money can you save by turning off your computer overnight?

I never realized that a good amount of money can be saved just by cutting the unnecessary wasted energy costs.

Note: This definitely isn’t applicable to everyone or every scenario but in some cases applying this technique can save a bit of money.

I have done a little experiment with the ‘MS6115 Mains Power Meter’ on my work desktop computer to find out the effect of wasted energy in an attempt to save some money by generating awareness. I am pretty shocked with the results to be honest seeing how much energy is wasted every year.

I have used the Dell Optiplex GX620 Desktop Computer for this Energy usage/cost calculation. MS6115 Mains Power Meter was used to measure energy usage. I have been doing various kinds of experiments with this power meter that i mentioned on my Essential tips to start living Green today post a few days ago.

Wasted Energy cost of a Desktop CPU (Dell Optiplex GX620)

A desktop CPU running idle with Screensaver consumes about 0.082 Kwh (What is kilowatt-hour, kWh?).
Energy Usage for overnight, 5pm-9am, 16 hours (Given an eight hours work day) = 0.082 x 16 = 1.312 Kwh
Energy Usage over five working day overnights = 1.312 x 5 = 6.56 Kwh
Energy Usage over the weekend = 0.082 x 48 = 3.936 Kwh
One working week Energy Usage = 6.56 + 3.936 Kwh = 10.496 Kwh
Energy usage over one year = 10.497 x 52 = 545.792 Kwh
Average Energy cost per Kwh = 11 cents.
Annual Energy Cost for the Desktop CPU = 545.792 x .11 = $60.04

Desktop Computer Energy Usage

Appliance name

Energy (kw)

Overnight energy usage

5 days energy usage

Usage over the weekend

Working week usage

Annual energy usage

Desktop CPU running onidle with screen saver







Monitor running on screensaver







Appliance name

Average cost per Kwh

Total cost

Desktop CPU running onidle with screen saver



Monitor running on screensaver





Wasted Energy cost of a Monitor (19 inch Dell Widescreen monitor)

A 19 inch widescreen monitor running on screensaver consumes about .05 Kwh energy. Using the calculations used for the Desktop CPU the Annual Energy Cost for the Monitor = 332.8 x .11 = $36.6

Total Wasted Energy Cost

Total Annual Energy cost of the computer (monitor and the CPU) = $60.04 + $36.6 = $96.64
For a company with 100 employees the annual energy cost = $96.64 x 100  = $9664 !

So, that’s a rough estimation of how much money ($9664) the company can save if the employees just turn off the computers when leaving for home at the end of the day. Imagine all the big companies with dual monitors, powerful CPU and thousands of employees.

Does it really make any difference? I think it does in some cases.

Comments (15 responses)

  1. bob says:

    Great cost breakdown thanks!
    Companies can actually schedule pc’s to boot up at say 5 am on LAN and do all the updates, scans, etc. So pc’s are ready when people arrive, all this talk of lost productivity is laughable especially when you look at how much time people spend on non work related activities on their pc’s ( amazon, facebook, youtube etc ). You want to save productivity, limit access to those websites to specific time windows in the day.

  2. Gabriel says:

    20min to boot up? I think that’s where the problem is so not really an excuse to not shutting down. Reduce those boot times, my workstation (which also has a long list of security and antivirus software) boots up in less than a minute. You could also consider turning on the computer before employees arrive automatically.

  3. Tim says:

    The problem no one here is recognizing is the affects of wasted energy as a whole. Look at this as your company giving back to the environment. While the wasted electricity doesn’t out weight the benefits (lost man hours) you will be saving the planet. This is eseentially what Aldo Leopold was asking of people back in 1948; saving the planet isn’t always the most cost effective method, but in the end if we don’t do our part we then our children won’t have a part. Every wasted Kwh is that much more pollution, toxic waste, habitat destroying damm or whatever else we use to create that energy.

  4. YesMan says:

    Every single suggested morning task requires a computer to perform effectively:
    –“Review notes from previous day”
    –“make plans for current day”
    –“return phone calls, or initiate phone calls”
    –“have a morning meeting to increase communication”
    No serious workplace is going to make “highly paid employees” wait 20 minutes to start getting work done, which is why IT maintenance activities are always autoscheduled to run overnight or on the weekends.
    With that said, with rare exceptions, most workstations should be left on 24/7, except when being transported (as in the case of dockable laptops). When leaving for the day, just lock the keyboard, then pick up right from where you left off the next morning. Sure, you could hibernate (which also takes some time), but then you lose the ability to run automated scans and backup processes, as well as the ability to log in remotely to address emergencies or just to check your email or work schedule.

  5. Greg says:

    Coosbane, if you’ve got highly paid employees sitting there staring at a screen for 20 minutes while it boots, and they can’t find something else to do during that time when they first get in, I think maybe you’re paying them too much.
    Review notes from previous day, make plans for current day, return phone calls, or initiate phone calls, have a morning meeting to increase communication while everybody’s systems are booting up if you have to.
    With the savings, you could probably upgrade people to SSD’s to drop down the boot time considerably as well. Not many people I know do full virus scans nightly, pick a night to have it scheduled, and get everybody on the same schedule and run them on that day.

  6. Coosbane says:

    My company has installed so much anti-virus, anti-spam, encription, anti-hacker, etc. that it takes at least 15 to 20 minutes for a startup from power off. Since our employees are paid more than the rate per kilowatt hour, it is extremly ineffecient to have highly paid employees stare at their screen for 20 minutes waiting to begin each morning. Overnight downloads and virus scans remove that burden from daytime processing, too. A weekend shutdown makes because there are benefits of a periodic cold boot anyway.

  7. RealityCheck says:

    Richard Burgess hits the issue right on the nose.

    Sure, 100 employees might be able to save close to $10,000 by turning off their computers all the time, but remember that their productive effort will be worth at least $10,000,000 (100 x $100,000 as a rule of thumb) to their organization as a whole, and if their productivity goes down by even 1% (for all the reasons Richard outlines), you’ve already lost $100,000 off the top.

    These kinds of pseudo-cost saving initiatives are popular with managers because it seems to involve the rank and file in “doing something” to help the company, but it’s as short-sighted as yanking the coffee.

  8. Richard Burgess says:

    One thing to keep in mind is that antivirus scans and windows updates are best run overnight as if they are run during the day they can slow down productivity on the desktop and reduce productivity across the board (would be interesting to see a study on this as well if you are thinking of doing another). If these scans are not done however you are leaving your network open to virii, hackers and problems. I would advise comparing the cost of that down time which could potentially be hundreds of dollars a MONTH vs leaving it on overnight during the week (i would recommend turning the machines off over the weekend however and then perhaps having one person come in early on Mondays to turn the machines on and let the scans run before normal business hours. Or setup an automated process for this.).

  9. K. Nye says:

    Our school district uses a server based program to force PCs to shutdown either at a set time or after a configurable amount of inactivity. It’s very flexible, versatile and reasonably priced. Check out AutoShutdown Manager. Tech support is responsive and helpful too, though I really only needed a few questions answered while setting it up on one of my domain controllers.

  10. Model Planes says:

    I enjoy what you guys tend to be up too. This kind of clever work and reporting! Keep up the fantastic works guys .

  11. Thank you for quantifying the amount of savings per computer. I had no idea that a Dell Optiplex would cost an additional $100/year if left on all the time.

    Great job on the calculation breakdowns!

  12. 3D Printers says:

    Hi,, i am trying to implement this power saving technique for my call center. lets see how it works…

  13. Umesh says:

    Actually I am trying to implement power saving techniques for my office which has 50 computers. Is there any central tool to implement using AD policy?

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