i did some work about 10 years ago designing a tumble dryer for a well known home British appliance company (almost all their products suck
).
As part of the development process we looked into various other models including the AEG heatpump models and i have to say they were superbly built. The insides were like a watch, not a finger mark on any of the (many) internal stainless parts compared to the US (Maytag etc) driers which looked like they were built on scrapheap challenge, all poor quality pressings and blooby welds.
At the time the AEG's were about a grand and pretty much twice the price of anything else around.
An important point is that the energy ratings A-G are on a different scale depending on whether the dryer is a vented (white duct you have to put thru the wall) or condenser.
Lots of condensers had B or A ratings whilst vented had Cs and Ds but if you looked at kW used per kg of clothes dried the vented dryers used less than the condensers.
The difference was primarily due to the fact the vented units were using the heat from the house as well as the electricity. If you heat using gas then it's possible that this is a good thing. If you disconnected the electric heaters you would effectively have a gas tumble dryer.
I wonder if a dryer vent could be plumbed into a MHRV system?
A condenser dryer will effectively act as an electric heater in your room so if you have MHRV it may make some sense.
Another factor is that condenser dryers are much less reliable than vented dryers (more gubbins to break). A vented dryer can last for years (my parents one is over 25 years old and still going). So if you are just going to use a dryer occasionally for emergencies a vented dryer may make more sense in terms of capital cost, reliability and embodied energy.
