Watt

A watt (W) is a unit of power equal to 1 Joule per second, where a Joule is a unit of energy.

A big apple falling from a tree hits the ground with an energy of about 10 Joules. So if apples fall out of the tree at a rate of one/second, the power hitting the ground is 10 watts.

Electricity generation is measured in KW(kilowatts), MW(Megawatts) and GW(Gigawatts),
where 1KW = 1000 W, 1MW = 1000 KW, 1 GW = 1000 MW.

Electricity consumption is often quoted as KWh (kilowatt. hours).
The average US household consumes a daily 30 KWh, averaged over the year.
Storage is often measured in MWh(Megawatt. hour), GWh(Gigawatt hour) and TWh(Terawatt hour),
where 1 MWh = 1000 KWh, 1 GWh = 1000 MWh and 1TWh = 1000 GWh.