I'm asking this here because this is primarily a huge office scenario and administrators will more likely have the answer I'm looking for.

Employees' desktop computers can be either left turned on for the whole night or switched off in the evening and turned back on in the morning. The latter will surely save energy. In the same time turning on and off is very harmful for the equipment - hardware often breaks specifically when turned on.

Both energy and hardware replacements cost money. With energy it's quite obvious - you pay every month according to what your power meter shows. With hardware replacements it's worse - you need qualified stuff to quickly diagnose the problems and once something breaks the affected employee will have to wait for some time while his computer is fixed/replaced and the data is recovered.

So the company has to choose between saving money on energy and saving money on computer maintaince and lost hours. Such decisions must be well though.

Is there any detailed study of how turning computers off each evening affects their lifetime?