It is somehow possible to calculate it. You need to know some details of the car. I might be wrong after all but here is an idea:

We should distinguish the forces.

- First of all the force to move the car forward. I will call this

**F**_{C}- Also, the increment of the force when the car is climbing a hill. This i will call it

**F**_{H}. To make things easier i suppose that we are not discussing for a rally Acropolis car and the driver will not step on the gas while going don the hill.

- The force to eliminate the air drag. This force i will call it

**F**_{A} (and i found it from an auto test company)

- As for the turns, it is known that the friction is significantly increased and the efficiency of the motor and the gears to divide power is significantly decreased. But i will not calculate any of these. I will suppose that the driver is not stepping on the gas pedal when turning (safety first

)

Some parameters i will use:

V : The speed (velocity) of the car

g : 9.81 m/sec

^{2}, the acceleration of gravity

M :The mass of the car in Kgs

q : The coefficient of rolling resistance. This is a typical value for new vehicles from 0.009 to 0.016

A : The surface of the front of the car that causes air drag in m

^{2}p : is the density of the air, approx 1.2 kg/m

^{3} at sea level at normal temperatures

C : the Drag coefficient of the vehicles. A normal value is 0.36 to 0.39

s : The slope of the hill the car is climbing, in %

E : Energy

t : Time

Now to calculate these 3 forces:

Force to move the car forward. The car has to elimenate this force in order to move:

F

_{C} = q x M x g

The increment of the force when the car is climbing a hill. This force will be added to F

_{C}F

_{H} = s x M x g

The force to eliminate the air drag:

F

_{A} = 1/2 x C x A x p x V

^{2}Our car has to generate enough power to elimenate all these drags. To calculate this power we should have in mind that:

(1) W = F x d that means Work = Force x distance

and

(2) P = W / t that means Power = Work / time.

(2) because of (1)becomes P = F x d / t

but (3) d/t = V so

(2) because of (3) becomes

**P = F x V**So:

P = F x V =>

**Pol = (F**_{C} + F_{H} + F_{A} ) x VThe above formula wil calculate the generated power for a given car at given speed in Watts. You may use the

Power unit converter to convert this value to any other unit you want. But this will calculate the power for a car that is moving in

**constant speed** straight or climbing a straight hill. Also, you must have in mind that all the forces that i added before must have

**the same direction!!!**. So, if there is an air blow from the side of the car or the car is turning, you should calculate the Fol of each force.

In case the car is accelerating, you should use another formula t calculate the power generated as the speed is not constant.

First to calculate the energy:

E = 1/2 x M x V

_{2}And from the energy:

P = E / t, where t is the time needed to accelerate to a speed. The P is also in watts. use the

Power unit converter to convert this value to any other unit you want.

So it comes that this gadget should have an accelerometer, a speed meter and a meter for the angle of the road to climb... It could be possible.