Renewable Energy trading using Blockchain

Want to implement an environment where there are houses with their own solar panel system, whatever they produce extra will be converted into "coins". These coins are equivalent to 'x' KWH amounts of energy. This happens in a cycle of a month (or a day). So at the end of the month whoever consumed more than they produced have to pay up. Those who produced excess have coins which are backed by the money others pay up. If the community as a whole is lacking energy then that is taken from the utility grid. (I have the math figured out) However, the challenge is to keep track of the movement of each of these energy coins produced using blockchain.