It is simple maths...

E = 0.5 * m * v^2

Where m=mass, v=speed.

An object running with m having mass m carries energy E.

P = E / t (for continuous power)

Where t=time and P=power

So, using acceleration (which is is counted in speed/time^2) you finally, after some cooking, you get to the point you want. You only need to know the mass of the car but that's easy.

Also, take care of the units to use with these formulas

I have not test it but i have faith in maths