What would i use to measure watts being consumed?

i am building a display for a project to demonstrate the electricity usage for a LED bulb vs an Incandescent and a CFL. I believe that i need a wattmeter, but cant find one online for a reasonable (cheap) price. i have found an ammeter for a good price, but im only trying to demonstrate the difference between a 100 watt, 32 watt, and a 7 watt bulb, and would like to be able to demonstrate the usage, rather than just referring to the package. any ideas where i could find one of these or any ideas?