I have just got a heat pump drier to replace the vented, main reason was easy to put the small drain pipe of the heat pump in with the washer drain and can put the drier on top of the washing machine, and so I can now close the window in the utility room, and stop bolting the utility room door. I did not want to bore a large hole in the wall for vented as each one we have had seems to have the vent in a different place.
But the big difference with efficiency was the vented had no sensor to know when dry, and it had two heat levels, the reset for over heat was at the back so hard to reach, so we always used the lower heat level, so time wise it seems the new one is as fast as old. However new Haier HD80-A2939S seems to be ripping and toggles etc off the cloths, they seem to get caught in the lint trap, which did not happen with the old drier.
Also controls are more complex, a 15 option dial, and 6 buttons, compared with simple high/low heat, and a timer. So to compare is not really fair as it is not only the method of extracting moisture which has changed. I am sure the vented one often ran longer than required.
It seems we have different types of condenser driers, the one we have in the garden room is built into the washer, I uses cold water to condense, and heating element to heat air, main advantage is don't need to move cloths, the drier is built into the washer.
But we have stand alone condenser driers, and heat pump driers, and again it seems some still use elements to heat the air, and it seems hard to get information about condenser driers v heat pump driers, or even compare makes, when we bought ours we were shown a selection of units, some you needed to remove the whole condenser to clean, others just filters, we were careful to select one with option to connect a water drain, but noted it does not use the tank when using drain, so if the water was drained to outside, would it freeze? I note central heating boilers with condensate drains store up the water then release it in batches to avoid it freezing.
Theory the vented drier should work better in winter, as the air is colder so retains less moisture, but wife tells me this is not the case, even when the air is drawn from outside, if drawing air from inside, big question is will it cause enough depression to draw exhaust fumes into the house from any open vented fire? Same applies to bathroom extractors and cooker hoods, it depends if there is enough ventilation in the house. Clearly not a problem with a pipe out of an open window, but with hole bored in wall, needs to be considered.
The open window in a unheated room should not have been a problem, but only if the user always closes the utility room door. I have walked into our kitchen and realised the utility door left open, and kitchen very cold, even when drier not in use, as window was always left open, so even when used in a unheated room they can still cost money due to loss of central heated air.
As to time taken to dry cloths, does not seem to be much difference between heat pump and vented with the vented on low heat setting.
I thought a condenser drier other than those built into washing machines all used heat pumps, seems I was wrong, mine is it seems A++ Weighted Annual Energy Consumption (AEc in kWh/year) 265 kWh/annum [Based on 160 drying cycles of the standard cotton program at full and partial load, and the consumption of the low-power modes. Actual energy consumption per cycle will depend on how the appliance is used.] there are models down to 200 kWh/annum.
I did consider outdoor drying, however it means more rewashing due to soot and bird lime, so likely does not safe energy. Would need a car port or similar so could dry even when raining.
