I think Voltbox is just another scam. I am a professional electrician and have worked in the field for many years, even had an electrical contractor's license. I spent my greatest number of years in the field working as an electrical technician and troubleshooter and I can tell you that everything in a building, be it a house or otherwise, requires so much power and you get billed for the amount of power you consume, not for capacity, current or anything else.
There is a power equation and you can manipulate any part of the equation but on the other side of that equation, you will have total power needed or consumed and that will not change, unless you want things not to work or wear out sooner than they were designed to.
I can get a 120V light bulb to work for at least a short while, but if the voltage is too much, the thing will burn out. I can play around with the current but things will either not work or stop working soon.
There is really only one way for anyone to save on electricity and that is not to use it, period. If anyone really wants to save on electricity, then use only one or just a few solar panels to create your own electricity. Solar panel systems can be custom-designed to serve the needs of just one or a few circuits but one does not need to spend $20,000 for an entire house system. A product like Powerbolt is not going to get you anywhere.