We estimate that a Wi-Fi router uses 2 to 20 watts, with 6 watts being average for a wireless router.
With the average cost of electricity being £0.19 per KWH and the router being on for 24 hours a day we arrive at the following calculations:
Cost Per Hour: £0.0011
Cost Per Day: £0.0274
Cost Per Month: £0.83
Cost Per Year: £9.99
kWh Per Day: 0.14