Harry I wouldn't worry to much about the watts mate, if you take the average price per kWh (unitof electricity) and do some maths we can calculate how much this would cost to run
So the average price of a unit is about 7p I belive so we take this and times it by your wattage
7 x 86 = 602
now divide it by 1000 ( because a unit is a KILOwatt not a watt)
602 / 1000 = .602p per hour to run
so over a day
.602 x 24 = 14.4p per day
this may vary depending on your unit price
ps an average light bulb is 100w
So the average price of a unit is about 7p I belive so we take this and times it by your wattage
7 x 86 = 602
now divide it by 1000 ( because a unit is a KILOwatt not a watt)
602 / 1000 = .602p per hour to run
so over a day
.602 x 24 = 14.4p per day
this may vary depending on your unit price
ps an average light bulb is 100w