A 500w halogen security light if left on constantly for an hour costs on average 17 pence.
A 500w halogen light produces on average 9,200 lumens of light.
In comparison a 50w Led security light, if left on constantly for an hours costs on average 1.7 pence.
A 50w LED security light produces on average 4900 lumens of light.
The above estimates are costing electricity at 34 pence per kilowatt.