Power meter(watts) and a way to store values

Hi guys! Im doing a project for school(physics) and I have choosen to do a research about the relation between power in electric motors and the weight it is carrying. I need some help to decide how I am going to do it, first I need a non-invasive sensor but idk which one will work better. And I need suggestions for a way to store values(watts) because after that I am going to be doing graphics and all that. Thanks! :)

I think we need to know what kind of motor. AC squirrel cage induction? 12 V PM motor?

What Volts? What amps?