You haven't told us the "wattage" rating of the bulb. We'll just have to call it ' W ' .
The bulb uses energy at the rate of W watts, or 0.001W kilowatts.
In 12 hours, it uses 0.012W kilowatt-hours of energy.
= = = = =
W watts = W Joules/second
1 hour = 3600 seconds
12 hours = (12 x 3600) seconds
Energy = (W Joule/sec) x (12 x 3600 sec)
Energy = 43,200W Joules
