We are the new kids on the block (Time Off – B 44), and this subject is one which has been significant for us.
The yacht has just been lifted ashore at Hayling Island having the hull strengthened because Bavaria yachts do not use enough laminate in the keel area, at least in some of the boats.
The yacht will be ashore for 4 months or so, with all the kit on board, and we asked the repairers if we could put a dehumidifier on board. They were a little reluctant because of the safety aspect, having heard of failures which resulted in fires and damage to other yachts. Their advice / requirement was for a good quality unit, such as an EBAC, but they came up with an acceptable alternative – a tube heater (which some of the chandlers have in stock), supplied by them. Of course we all know that the principle is different, but the yard experience was that the tube heaters are very effective in providing background heating through the Winter and thus keeping the interior dry.
On previous yachts which I always kept ashore for 6 months during the Winter, and in one of the dampest areas of UK (S. Devon), I used an EBAC, draining directly to the sink, and this kept the yachts dry and without damage. In fact dry enough to varnish the interior.
I would seriously consider my Insurance terms before using a dehumidifier!
I hope the above may be of some use.