One kilowatt hour is equal to

One kilowatt-hour (kWh) is the commercial unit of electrical energy, representing the energy consumed when one kilowatt of power is used for one hour [2]. To convert this to joules, the standard SI unit of energy, we multiply the power in watts by the time in seconds. Since 1 kilowatt equals 1,000 watts and 1 hour equals 3,600 seconds, the calculation is 1,000 W!! 3,600 s, which equals 3,600,000 joules [1]. In scientific notation, this value is expressed as 3.6!! 10^6 joules [2]. Option 2 (36!! 10^5 joule) is mathematically equivalent to 3.6!! 10^6 joule, as moving the decimal point one place to the right decreases the exponent by one. Therefore, 1 kWh equals 36!! 10^5 joules.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > 11.8 ELECTRIC POWER > p. 191
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 11: Electricity > What you have learnt > p. 192