The energy firm wants businesses to save energy and reduce CO2 emissions.
The Carbon Trust claims that the average office wastes around £6,000 a year by leaving office equipment such as computer monitors and photocopiers on over the weekend.
This contributes both to financial wastage of around £6 billion in total - as well as significant increases in terms of the amount of CO2 released into the atmosphere.
"Small steps can make a big difference," Npower spokesman Nigel Alcock commented.
"If everyone gets involved in joining the Big Switch Off this August bank holiday and turns off their unused equipment, the combined financial savings and emission reduction could be significant.
"We want to show that saving energy can be simple and easy for everyone to play their part."
Click here to run an energy price comparison, and see if you could be paying less for your gas and electricity.