I once was in a discussion with my work colleagues about whether to leave our computers on or off when we go home at the end of the day. Being a bit of an environmentalist, I was of the opinion that the computers should be turned off. My colleagues, however, were quite adamant that on power up, the computer consumes so much power that any savings I would have gotten from turning them off overnight would be wasted. I have no idea where they got that idea but I was not able to convince them. These are quite techy IT people but I guess electronics was not their strong suit, but that applies to me too.
I looked for websites to back up my opinion and found this: Here, “Mr. Electricity” shows the typical energy consumption of some common computer models. He also has a question and answer page here where he recommends using a kilo-watt hour meter to see for yourself that no, “it doesn’t take extra energy to start up a computer”. I think the kilo-watt hour meter is not fine-grained enough to show it but other sites have shown that starting up a computer does require slightly more electricity i.e. up to about 70 more watts than their idle load, but remember that this only happens for a few seconds while the computer is starting up. A typical computer uses less than 300 watts while idle.
I’m reminded of the Mythbusters episode where the show tried to find out if “the energy to turn on lights exceeds the savings of turning them off”. They found that with a 90 watt incandescent bulb, leaving the light on instead of turning it off would only pay off if you were going to turn it back on within 0.36 seconds! When extrapolated to computers, this figure should be only a few seconds worth, so it is still not worth leaving your computer on.
There is also the argument that the life of the computer will shorten with the higher amount of power cycling. Mr. Electricity says that computers are not that fragile and will easily pass into obsolescence (about 2 years) before it fails from power cycling. I can confirm this as I have been shutting down my computer frequently and they have lasted me for years.
Some argue that Windows start too slowly and they don’t want to wait for the booting to finish so they don’t turn their computers off. With the faster computers these days, Windows usually starts within two minutes, and with the use of hibernation (where the computer saves its state so that the next time you start the computer, it returns to the same state as when you hibernated), you should be able to have Windows ready within 30 seconds, or at worst, within 1 minute.
The thing is, there are so much urban myths and “common knowledge” out there and it takes a bit of analysis to realise that, sometimes, what you thought was true may have no basis in reality.
I really should make a few more posts like this. My colleague was using his phone until it was almost dead because of the “memory effect” in rechargeable batteries. Actually, the memory effect only affected Ni-Cad (Nickel Cadmium) batteries. Most phones these days use Lithium-polymer batteries and somewhat older ones use NiMH (nickle metal hydride), both of which do not suffer from the memory effect.
