It’s a very boring thing to spend money on, but a dehumidifer can come in handy. In my case, even leaving the windows open a crack all day, leaking expensive heat out, I have a condensation/mould issue in my bedroom. I suspect part of this is the ridiculously short over-run time on the fan in the adjacent ensuite, but in any case, older houses with retro-fit insulation and double glazing can suffer from this as they will have less air flow than they did when built.
Meaco are a Which-recommended brand, so I bought the baby unit for home.
It pulls a surprising amount of water out of the air - about 2.5 litres every 24 hours or so - but it has completely eliminated the condensation, which I suspect should translate to no more mould. It uses a unit of electricity about every eight hours, which stacks up to quite a lot of money at today’s prices - however, that’s only if it runs constantly.
My suspicion is that it probably only runs for 6-8 hours out of every 24, which is not too bad. The cost is also offset by the gas savings from not letting all the heat out during the day, although you do still want to think about changing the air now and then.
“Night mode” is too noisy to sleep in the same room as (in my opinion), so I tend to turn it off before going to sleep, and back on in the morning.
We also bought their biggest unit for work when we had a damp problem caused by a leaky roof, and that seems to suck moisture out of the air at a decent rate as you’d expect.
Too early to comment on long-term reliability, but overall, seems well built and gets the job done.