A recent study by Fujitsu Siemens claims that about $217 million (123 million pounds) is wasted every year in the U.K. alone powering PCs that could have been shut down or left in hibernation mode. The report also pointed out the environmental impact of all the wasted energy.
Though the study involved generic PCs, its results are also valid for Point Of Sale systems. Many shops leave the POS terminal running during the night, in order to start working directly when opening the shop the next morning, not realizing that they could save an significant amount of money on the energy bill.
Switching off POS systems has another benefit: many POS software perform maintenance tasks when shutting down or starting up the system. This might even include tasks as sending the Z reading to the central office or importing new price lists into the system. By switching off the system every night, you make sure that these tasks will be performed.
Some people have claimed that regularly turning computers off can, over time, weaken links between components and damage hardware such as the hard drive. This fact has not been proven yet, and most certainly is not true in POS systems without moving parts as hard disks and CPU fans.