Electric power and Commercial unit of “electric energy”

# Electric power = (Energy consumed)/Time

  
    P = Heat/time

    P = (I²Rt)/t
    
    P = I²R ------(1)
Or,
P = (R.I)×I

By ohm's law, V = R.I

P = V.I

Again, V = RI
            V/R = I

Hence, P = V×(V/R)

P = V²/R

SI unit of electrical power is
Joule/second   Or   watt (W)

Other bigger unit of electric power and their relation with watt
1 kilowatt = 1000 watt
1 megawatt = 10^6 watt
1 gigawatt = 10^9 watt
1 horsepower = 746 watt

# Commercial unit of “electric energy”

1) watt hour =  one watt hour is the energy consumed by an electric appliances having power 1 watt in 1 hour.

1 watt hour = 1 watt × 1 hour
1 watt hour = 1 Joule/second × 3600 second
1 watt hour = 3600 Joule

2) 1 kilo Watt hour : 1 kilowatt hour is energy consumed by an electric appliances of power 1 kilowatt in 1 hour.

1 kilowatt hour = 1kilowatt × 1 hour
                       = 1000 watt × 1 hour
                   = 1000 Joule/second × 3600 sec

1 kilowatt hour = 3600000 Joule