The cost of an energy harvesting element that converts ambient energy into electricity is only part of the cost of employing such a solution because the power may need to be stored, smoothed and converted into the right form of electricity such as ac or dc and high or low current etc. The element casts vary from a few cents for photovoltaics on a calculator to millions of dollars for photovoltaics on a space vehicle. There is a trade off with many other parameters for a given application, one being life.