The discussion of Kw and Kw/h sometimes is 'the cart before the horse' and I find it easier to understand when it's approached as an energy conversion (energy cannot be destroyed, just changes state) and thinking of kilowatts as an end product, not a stand alone unit.

From a mechanical point, to rotate something takes 2 things; torque (in ft/lbs or N/m) and rotational speed (RPM). This can be converted into a horsepower (HP) rating (thank you James Watt). HP can then be converted into watts (1 HP = 746w) which can then be converted into electrical energy terms known as 'true power' (I am not going to bring in apparent and reactive power as that is a whole other component that can be discussed later).

For heat energy, one Kilowatt of heat per hour = 3415 BTU/hr

From a chemical point, batteries use a chemical reaction to create an electrical charge at a certain rate (Amp/hour) and to charge them takes a certain rate of charge.

In electrical terms watts are a

**product**of Voltage (E) and Current (I) - W = E x I (coulombs got mentioned earlier )

Let's say a charger uses 10 amps at 120V - 120V x 10A = 1200w or 1.2Kw

If it uses the 1.2Kw constantly for 1 hour then the rate of usage is 1.2Kw/hr. If your car takes 10 hours to charge - 1.2Kw/hr x 10 = 12Kw/h

If your power authority charges $0.15 per Kw/h - 12Kw/h x $0.15 = $1.80 cost of charge

Using a 240V, 16A charger - 240V x 16A = 3840w or 3.84Kw. Using the 12Kw/h (what was needed to charge the car) / 3.84Kw = 3.125 hours charge time (greatly reduced)

3.84Kw x 3.125 hours x $0.15 = $1.80

Unfortunately, batteries cannot be consistently charged at a high rate until fully charged. The charging system slows down as it approaches full charge so the calculation can't be applied directly as the voltage and current are increased.

Oh yes, Kilowatt is a metric unit