Around 10W I'd say.
So assuming your router is on 24 hours a day, you're looking at 10*24=240Wh, which is 0.24kWh.
With the electricity price in the EU maybe reaching EUR 0.2/kWh, you're talking EUR 0.04 a day. Even if the electricity price doubled to EUR 0.4/kWh you would be looking at EUR 0.08 a day.
With the electricity price in the EU maybe reaching EUR 0.2/kWh, you're talking EUR 0.04 a day. Even if the electricity price doubled to EUR 0.4/kWh you would be looking at EUR 0.08 a day.