There are many sources of electricity available nowadays. In addition to a number of Utility distributors, there is also sun, wind, various co-generation options, etc. Power can also be stored in batteries, facilities or cars. However each of those sources has it’s specifics – the sun doesn’t always shine and wind doesn’t always blow, a battery can get empty… Utility grid is always available, however, power from the grid may be expensive. The challenge that we face next is – how to use those power sources to get the most of them and to justify the investment.