Why would a lower voltage save money?
Power is the same, slightly higher current requires heavier wiring.
Well of course dropping your mains input voltage would save you money. You pay by the kilowatt hour consumed. Watts is equal to voltage X current, lower voltage = lower watts. If an appliance draws 1kw at 240volts if will consume 4.166 amps, as a 57.6 ohm load. The same load supplied with 220volts will draw 3.819 amps or 840 watts. That is 16% reduction in power consumed.
Now if the appliance will work as well at 840 watts Vs 1000 watts is another story altogther. Lights would be a little less bright for sure.
Lefty