Electric car how many watts it uses at crusing speed of 60 mph ??

Question

assuming the car weighs appr 3500 lb

Answer 1

There is 745 watts per horsepower.  So if a small 90 horsepower car could cruise at 60 mph at 1/3 its max output you would have 30 HP x 745 watts/HP = 22,371 watts.  22 Kilowatts.

This is just a guess.  You would have to know many things about the car to really be accurate.  At 60mph the most work is being done overcoming air resistance, so a streamline design would take less than a boxy pickup truck.  The rolling resistance of tires also causes the engine to work, so tire design and inflation play a role also.