WHS is designed to run 24 hours per day, particularly so client computer backups can be made when they are not being used. However, dependent upon the network card tou have in your Server, you could try using Wake On LAN (WOL) software on a client to wake
up the server from sleep when you need to manage or use your server.
Phil P.S. If you find my comment helpful or if it answers your question, please mark it as such.