For a 7kg wash at 60 Deg C (the programme used), an A-rated model must use 0.19 kwh/kg or less (1.33 kwh).

The drying part of the cycle will use much more energy than the washing cycle. The best available washer dryers are B rated for the whole cycle and will use around 0.8 kwh/kg to wash and dry a full load. For a 7kg load that is 5.6 kwh. So if 1.33 is the wash, then 4.27 kwh is the drying.

If you use a lower temperature wash the energy used in the wash cycle will of course be lower, but drying will still use the same.

Not all machines adapt well in terms of energy use to only washing a part load, so for best efficiency always wash with as full a load as is feasible. The drying cycle will adapt if the machine has a sensor to detect the dryness and end the cycle, timer ones don't.

Best wishes
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icemaiden