What benefit does a humidity sensor give?

I'm buying an extractor fan for a bathroom with a new shower. I'm interested to find out what the benefit will be of doubling the cost of the unit to £160 of a humidity sensor?

I haven't got one but at a guess, the humidity sensor would be there to turn the fan on/off according to the humidity level to limit humidity and hence prevent/reduce condensation. So probably an advantage for rooms with humidity issues - bathrooms/showers, kitchens. Not much use where the fan is used purely to remove odours - toilets.

£160 sounds a lot, have you had a look online - Screwfix, Toolstation etc?

The benefit of a humidity sensing extractor fan, as opposed to a timer-based unit, is that it will only run when it's needed to get rid of the excess humidity following a shower.

Timer-based ones which are linked to the light switch (as is normal) will come on every time someone goes into the bathroom, even if there's no need for them to do so, leading to unnecessary noise and to the fan chucking nice warm air out of the house for no reason.

So, humidity sensor based ones will save money in fan running costs (fairly trivial), heating costs (slightly less trivial) and reduce unnecessary noise.

I'm not sure if that's worth £80.

Our en suite bathroom has a pull-cord extractor fan with a timer, so at least it only comes on when we choose to switch it on when having a shower.

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