Thanks for your reply @hobo.media.
My preferred unit is a unit of electricity = one kiloWatt-hour, sub-divisible to maybe to one Watt-hour, seeing that a very large portion of possible users will be familiar with this unit and electric energy is a form of energy that is widely used in production and easily measured with meters widely available.
With the price of electric energy being only a fraction of a USD, I guess, comparing values of tradable items in USD, that it would not make much sense dividing it into smaller units for popular use. (A Watt-hour currently costs around 0.01c in California, I believe)
What do you think?