Energy is the capacity for doing work. It exists in potential, kinetic, thermal, electrical, chemical, nuclear, or other various forms. The energy always will be, Heat and Work, in the process of transfer from one body to another. After it has been transferred, energy is always designated according to its nature. Hence, heat transferred become thermal energy, while work done will be in the form of mechanical energy.

Energy is typically measured in Watts which is = Joules/second and 1 Joule = 1 kg m2 / s2

Because 1 Watt is considered small measure and to make Energy numbers useable, Engineers use multiples of thousand watts, like, Kilo, Mega, Giga and Terawatt.

One more confusing thing will be to differentiate between the "Instantaneous" and "Total Energy" use. For the Total Energy will require hours be added to the units like on the Energy bills.

Here is a list to make things clear and easy

Watt (W): An energy saving light bulb nowadays uses 6 watts (6W). if you keep it on for 12 hours it will use 72Wh.

Kilowatts (kW): This is equal to 1000 watts, used for domestic energy. A domestic electric oven uses 3kW and if you use it for 2 hours uses 6kWh.

Megawatts (MW): Used for power generation and distribution. An average gas power station generates 300 to 700 MW. In Bahrain Al Ezzel gas power plant generate 950MW, so in 2 hours it will generate 1,900MW.

Gigawatts (Gw): This unit is used to describe the national demand. The typical instantaneous demand for Bahrain top estimates has peak demand reaching around 4.5 Gw in the summer. While in Abu Dhabi in the (UAE) had a peak electricity demand of 10.2 Gw (2016).

Terawatts (Tw): This is a huge-number and used to describe big countries demand or country level consumption. In Bahrain, the total consumption was 26.11 TWh per year (2020).

Saudi Annual is 289 TWh

UAE Annual is 131 TWh (2019)

UK Annual is 310 TWh

The world consumption was around 23,398 Terawatt hours in 2018.