For drying clothes rapidly in wet or cold weather we use a luggable dehumidifier in the wet room, on an extension lead. Load is about 230W, nearly continuously, but it seems to pause dehumidifying from time to time and just be fanning. The clothes all go on a folding rack with the dehumidifier pointed at it. If there's a garment of interest, that's where the dehumidifier is pointed. They're acceptably dry after about 5-6h [yeah I know, this is all a bit vague]. Whatever the dehumidifier is pointed at will be dry way quicker than everything else so sometimes we just switch it off at that point.
I assume the efficiency is roughly equivalent to a heat pump tumble dryer as it's the same principle, but a bit less efficient as the room isn't sealed so we're drying the general environment as well.
I suppose not that much different, the dehumidifier is basic a heat pump, it cools the air so the water condenses out of it, then heats it again to remove the moisture out of the cloths, only difference is the space used to place the cloths to be dried, the heat pump tumble drier is doing the same thing, but more compact.
My daughter uses a cloths horse in the kitchen, not really a good idea as it means the humidity of all the rooms increases, but she does not do enough washing for it to matter, and this is the big thing, how much washing is done, and what else makes the rooms damp? For those cooking on gas they are already putting loads of moisture into the room by burning gas, so a vented tumble drier is getting damp air to start with, I assume the heat pump type re-circulates the same air? So how damp the room is does not matter. The washer/drier must be very wasteful, ours uses the cold water to cool the condenser, so not only a lot of electric but also water used.
We were told the heat pump drier took a lot longer, however when we swapped from vented to heat pump, in the main so we could close window, as we never drilled hole in wall, we found no change in the time taken. It was not only going to heat pump, but also going to auto detection of how dry, it was guess work with the vented drier, we had thought since they are in a unheated room, it would make very little difference, however we found kitchen which is heated, got warmer, when the utility rooms window was closed. Will guess wife was leaving the utility room door open?
However the main point is all homes are different, last home we were pumping out centrally heated air with the vented tumble drier, my father-in-law had a gas cooker in same room as vented tumble drier, so room was damper to start with. All the tests are done in a warehouse which is unheated, so the fancy energy charts mean nothing.
It may well be pumping air outside is good anyway, causing air changes, it could also cause a depression in the home, drawing in fumes from open flue fires, that is a poor name, as my old house the gas fire flue brick was sealed to the fire, however since the fire draws combustion air from the room, it is classed as open flue. And a depression can still draw combustion products into the room.
The problem is we try to draft proof, then fit bathroom extractors, cooker hoods, and vented tumble driers, all sucking air out of the house. OK my house I am OK, still have an open fire, although not used except for the AC hose on really hot days, and as said unheated utility room, and large house so today sitting at 44% humidity in my bedroom, likely lower elsewhere in the house. But not that many people live in a house this size with only two people.
