Originally Posted by sccr64472
What you're failing to factor in is that the entire "startup" lasts for a few seconds. If you're talking about pure power consumption, then it's best to turn a computer off when not in use. However, turning on electronics is harder on them than running idle. Also, immediately after a shutdown, your computer will heat up due to no fans cooling the parts.
Here at work we have made several studies to determine MTBF (Mean time Before Failure) and one of the studies concerned with delicate sensing instrumentation (akin to computer hardware) in hazardous areas. When power was removed form the enclosures, the fans stopped working, as well as the instrumentation. We measured the temperature changes from in-use, idle, and off states to find that the highest temp is in the in-use state, and there is no statistical significance to the temperature difference between idle and off. Idle is contant temp, where off has a few minutes where the temperature remains constant, then starts to decrease.
I performed this same study on my HTPC and had similar results; so in conclusion, shutting down the computer reduces the stress induced by the system to its componets due to temperature.
There cannot be an increase in temperature as there is no heat source active.
Now, to addres that more power is needed during start-up of a computer, the short answer is yes. Fans, HDDs, floppies, optical and tape drives need to overcome inertia (they are not moving) to start spinning to their rated speeds. This requires more power for a short period of time (measured in seconds). A load of 533w (my gaming computer) can become 640w upon start up. Let me repeat, this is until all components come up to speed. Which is why PSUs should be sized 25% more than the actual load. This also affects the MTBF of the PSU, as more startups reduce the effective life of the unit (and the rest of the components).
Credentials: For those of you that don't know, I work for a Quality organization withn the biotechnology industry. I deal with chemical, mechanical and process issues every day. I am a Certified Quality Engineer, Certified Audito and a Professional Mechanical Engineer. So there...