I switched off the extractor fan in the bathroom. It was on a pull cord and we’d leave it on for 30 minutes or so after a shower. We have double glazing which allows you to fully lock the window whilst it’s slightly open to vent the room. I’ve read extractor fans use quite a bit of electric.
I’m a spark and fitted an exhaust fan on the exterior (only a vent cover inside) a couple of years ago. It clears the bathroom in no time especially on high. I think it cost around £75 trade (£110 retail)
A ventaxia 4″ silent extractor fan uses 3.2w on low and 5w on high. Where as a centrifugal fan uses 19w. 1Kw of electricity is equal to 1000watts. Taking the centrifugal fan uses 19w it would have to be on for 52hrs to consume 1Kw of electricty 1000/19. On the otherhand a cooling fan can use around 40w (1000/40=25hrs runtime to consume 1Kw of electricity.
My advice is to run your bathroom fan during and after a shower for 20 – 30mins and then allow any condensation left to tricke out the window. You do not want to run the risk of condensation build up which can seap through plasterboard ceilings or bath room cabinets over time or run the risk of a mould problem especially in winter, that could prove more costly in the long run. Oh and ignore over exaggerated scaremongering articals in the media.
What bathrom fan do you have?
You can calculate most appliances by the same formula 1000/x watts. An electric oven or kettle will be in Kw, so for example a 3Kw kettle will say take 5mins to boil. you would have to boil it 12 times before it used 3Kw/h of electricity. 3Kw/h of electricity say =3 x 55p (Kw/h price)=£1.65 now divide that by 12, it costs £0.1375p each time you boil the kettle. ?