Energy

The word “energy” is used to describe many different things—how we heat and cool our homes, how we fuel cars, and even how we’re feeling on a day. Energy isn’t something that can be seen or felt, but you can see and feel the effects when energy is transferred from one place to another.

Energy is what makes change happen and can be transferred from one object to another. Energy can also be transformed from one form to another.

Power is the rate at which energy is transferred. It is not energy but is often confused with energy. The watt is the most commonly used unit of measure for power. It measures the rate of energy transfer.

 The Energy absorbed by a user or supplied by a generator is the Power (P) product for the time (t).

If the Power is calculated in Watts and the time in seconds, the Energy is calculated in Joules (J). Therebefore, Energy is almost always calculated in multiples of the joule, and the most used is the kWh (kilowatt-hour), representing the Power of 1 kW delivered for the time of one hour. The formula below shows how can calculate:

E = P * t (kWh)

 1 kWh = 1000 Watt; 1 hour = 3600 sec; so: 1 kWh = 1000 W * 3600 sec = 3.6 * 10⁶ J