What and how?
Household electricity consumption, per household, is already pretty damn low, so what and how can you be reducing it by 30% or more?
Electric heating is, and always has been, as near to 100% efficient as it is possible to get
Most modern electronics are constant power devices so any changes to voltage are irrelevant as they will maintain the same power consumption.
Removing storage heaters and fitting heat pumps, 30-40% saving is very realistic and often higher