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1. As I said, each computer is a little different. But when idling, the power consumption is typically a few watts max. Therefore, you are using more energy by taking a shower, than your computer in the whole day.

The hard disk spins with very little friction. Therefore, you will need most of the "juice" to power it up. Once it is idling, the energy consumption is minimal.

Cheers

2. Originally Posted by fatra2
Did you ever look at the energy consumption of your computer, when idling??? I would suggest to leave it on. Instead go and make yourself a cup of tea: which by the way will use more energy to boil the water, than your computer in a whole day!!!
Cheers
I would like to see your math for those statements.

Making a cup of tea needs ~90kJ of energy.
One of my (older) desktops needs 61W when idling. In a day of 8 hours that makes ~1756kJ. So you can make 19.5 cups of tea for the same amount of energy.

By idling I mean not heavily working on the computer: typing in a wordprocessor, browsing text-based webpages, ..
Gaming or doing audio/video/photo editing consumes a lot more energy.

Powering up that same machine consumes 100W for about 10 seconds, then it drops to 61W.
Of course every machine is different but my example above can be taken as a starting point for many Desktop computers.

3. Turning off the monitor sounds like an excellent idea. It's an old crt monitor, so it probably uses as much energy as a TV. The computer goes into some kind of suspend mode after a while, from which it takes about 15 seconds to fully wake up. I gather from what previous contributors have said that it doesn't use significant energy during this phase, so leaving it on probably won't do any harm. I think that more or less answers my question.

btw how would I find out the energy consumption?

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5. Originally Posted by hazel
Turning off the monitor sounds like an excellent idea. It's an old crt monitor, so it probably uses as much energy as a TV.
Indeed they are quite hungry..modern LED monitors are a lot greener consumption-wise.

Originally Posted by hazel
The computer goes into some kind of suspend mode after a while, from which it takes about 15 seconds to fully wake up. I gather from what previous contributors have said that it doesn't use significant energy during this phase, so leaving it on probably won't do any harm.
Yes, in standby mode your machine uses probably around 10-15W.

Originally Posted by hazel
btw how would I find out the energy consumption?
Either by searching online with your computer brand and model or by plugging in a electricity meter.
news.bbc.co.uk/2/hi/programmes/click_online/4929594.stm

6. I say turn it off...

If like me you go out early in the morning 5 days per week and come back at around 7pm - there is no sense in having a machine on throughout the night and most of the day doing nothing...

How long does someone expect their hardware to last? I've always started up in the evenings (or afternoons at weekends) and shut down at night/late evening. I have never had hardware die as a result of this. The hefty electric bill would probably outweigh the cost of a new motherboard/hard disk every few years.

7. Originally Posted by hazel
How often should you boot your computer?
I do a fresh boot and shutdown at least once each day, and sometimes I might shutdown only to reboot later on that same day, depending on how long it will be before I'm going to be back to that particular computer. If I were running a server, my boot/shutdown/reboot scheme would be very different.

8. I suspend to disk whenever possible, it saves time when "booting" back up. I use a laptop for most things, because they use less power. My workstation at the office is on 24/7 by necessity, but I always turn the monitor off when not using it.

I would say, if your computer will go for more than 24 hours without being used, turning it off is better.

But computers are too varied to be able to answer your question directly. The best solution is the scientific one: get a wattmeter (for example, this one) and plug it in series with your power bar. Gather data, and download it via the USB interface. Plot usage over several days and weeks. Record data for both usage patterns, the "keep it on as much as possible" pattern, and the "turn off and on every day" pattern.

9. @Rosch I checked (it's a Fujitsu-Siemens Scenic T) and found the values for 240V/50 Hz are 140W (active) and 30W (suspended). 30W is a trivial amount imho.

@Cynwulf. You obviously work for your living! I am retired and seldom out of the house for more than three hours at a time. If I worked to your timetable, obviously I wouldn't leave it on. I don't leave it on by night either unless I have to because of an overrunning update.

OK, problem solved. Leaving it on by day doesn't do any serious harm as long as the monitor is switched off. In the evening, the whole thing goes off as at present.

10. You can use this device called 'Kill-a-Watt' to find out how much power your appliances are consuming.
If you use your computer mainly for web browsing or word processing, an '8-watt PC' would be good.

11. btw how would I find out the energy consumption?
For me since I used to be a industrial electrician. I use a clamp amp probe like this.

If you have any friends with such a tool Hazel. You just clamp it over the crt or desktop cord going to your outlet. To convert amps to watts. Ohms Law (online link conversion)

or pen and paper formulas

V=Voltage
I=Amps
R=Resistance

V = I x R (Voltage = Current multiplied by Resistance)

R = V / I (Resistance = Voltage divided by Current)

I = V / R (Current = Voltage Divided by Resistance)

The conversion of Amps to Watts at fixed voltage is governed by the equation Watts = Amps x Volts

For example 1 amp * 110 volts = 110 watts

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