Electrical appliances we have that are heavy users of power generally have a heating element of some sort. Heaters, washing machines, cookers etc. Dropping the volts to those will simply mean they have to be on longer to do the same job.
Lots of more high tech things are already designed to run on a wide range of voltage. Due to actually working on a regulated low voltage supply. Changing the input voltage is very unlikely to make any savings that are measurable.