Originally Posted by

**Bloss** Confusing ain't it!

kW (kilowatt) = the measure of capacity or size of a generator.

kWh (kilowatt hour = the amount of power output generated (or used – that’s how we are billed) over one hour (that is: the size or capacity multiplied by hours of operation from the renewable power source by wind, solar, wave etc).

**A 1kW PV system nominally produces 1000 Watts each hour, a 1.5kW system 1500W each hour**

**I'll say it is confusing!**

The panels produce **energy**. The unit of energy is **Joule **(J). The **rate **that the **energy** is produced is **power **(Watts, W). 1 Joule/second (J/s) = 1 Watt.

Where the confusion arises is that electricity is billed as **energy**, but the unit isn't **Joule **(or Mega Joules), but **kiloWatt-hour **(kWh) pronounced "kilo Watt hours". Note, the product or multiplication - is is not a division or "per" unit (i.e. it is **not **"kiloWatt per hour").

1 kiloWatt (kW) = 1000 Joules per second (J/sec)

1 kWh = 1000 J/s x 1 hour= 1000 J/s x 3600 seconds

= 1000 J/[s]s[/s] x 3600 [s]seconds[/s] (striking out the 'seconds' in the numerator and the denominator)

= 3,600,000 J

= 3.6 MJ