Power

Ultra 10 with one 200G disk (as a firewall/gateway/small server)- Averages ~111watts.

1.2GHz Duron with single IDE disk (as a firewall/gateway/small server) - Averages ~110watts.

Dell Latitude C610 (ubuntu desktop)- Averages ~42watts.

Power is measured in "watts" (named after James Watt). The units are energy divided by time. One watt is 1 joule transfered in 1 second. 1 British Thermal Unit (BTU) = 1 055.05585 joules. Most electric companies bill in "kilowatt hours". If Power interests you, you should check out Ohms_law.