The little transformer that plugs into my Gamma Progression II ELS looks like it steps the wall power down to 24 volts and 2.5 amps. I don't know what that boils down to in terms of total power consumption or how this machine compares to other electric rigs, but there it is.
What is the cost per KwH in your area ? I doubt that it cost you more than 25 cents of power.
Oh if you look at the power supply you can calculate the consumption using the cost tool that major power companies provide.