Not wishing to offend the posters on this thread, but another example of a little knowledge being a dangerous thing.
In your house you will have a variety of electrical devices. Absent some power amps, most modern electronic devices use some form of switch mode supply, often able to operate over a very wide range of voltage to accomodate both US (110V) and Europe / Asia (230V). Changing the supply voltage will not change power consumption, the switcher takes care of that.
Resistive heating devices (cookers, fan heaters, hair dryers, incandescent lights etc) will definitely draw more power as the voltage goes up, but in turn they 'work' better - the power isn't lost. If it takes 2KW for 2 hours to heat a room in your house, then running the fan heater at a lower voltage will draw less power, but you need to run it for longer. No energy saved. Same is true of the cooker, the hair dryer and so on - more voltage means more power in, but also means more power out.
Incandescent lights are a more complex argument (becoming less important as the use of incandescent lights dies out). Higher voltage means more power in, but also means a brighter light. Arguably, at a higher voltage you could use slightly fewer bulbs to light a room - thereby using the same power as using more bulbs at a lower voltage. The issue with incandescent bulbs is life. Voltage dictates the temperature of the filament, the higher the temperature, the shorter the life (not quite true for quartz / halogen-cycle bulbs). This is not true for modern CFL or LED bulbs which have electronic drivers built into them and don't have the same voltage sensitivity.
So, ignoring power amps with a questionable choice of mains transformer, most things in your house will work pretty much the same, with pretty much the same overall power consumption within the rated range of mains voltage.
No 'optimiser' required.