Bulbs today are generally marked with two watt ratings:
A ‘classic’ bulb shows the wattage it runs at - and gave an indication of its brightness
e.g. a 60 watt bulb was general purpose, a 100 watt bulb was high brightness
A low energy bulb tends to show its ‘equivalent’ brightness wattage and in smaller print it’s actual wattage
Eg an LED 60w/9w takes 9 watts of electricity to be as bright as a classic 60watt and an LED 100w/11w uses 11 watts of electricity
On your electricity meter one unit of the dial is one kilowatt hour - 1000 watts per hour
So if you have a classic 100 watt bulb turned on for 10 hours (100 x 10 = 1000) then you have used 1 unit of electricity
For a classic 60 watt bulb to use 1 unit then divide 1000 by 60, which is 16.666
Your electricity price is for one unit. A bulb will cost you that in this basis:
A 100 watt bulb uses 1 unit in 10 hours
A 60 watt in 16 & two thirds (16 hours 40 minutes)
A 11 watt in 90.9 (nearly 4 days)
A 9 watt in 111.11 (about 4 and a half days)
Bulbs are an easy way to reduce electricity by swapping to LEDs
But they are a fairly low user in the household (it makes a noticeable difference across the country as a whole)
Have a nose around your electricals for their wattage. The actual consumption will vary, for example a fridge needs to cool down it’s contents then just trickle at a steady state unless you leave the door open, the kettle is a high energy user, but only for a short time and ideally only boiling as much water as you need