If you are a parent, you probably want to implement some basic web controls at home. OpenDNS is my first stop for this basic functionality. The basic service is free. You just change the workstations to point to OpenDNS' DNS servers. You put a free agent on the workstation to check in with your IP address from your ISP to compensate for the changing DHCP address that most users have at home.
Should you leave your computers on at night or shut them off when you go home?
The answer is "it depends".
There are many factors that go into this decision. However, you may be wasting significant amounts of money by not properly evaluating and appropriately managing this issue.