In the market place the difference between buy and sell bids is called the spead.  Each square in the figure represent a block of electricity  placed on the market place. Either to be bought or to be sold.  Several block placed on top of each other indicates that there are several bids at the same price.

An interesting finding is that a small spread leads to a larger portion of electronic commerce.
A large spread gives a buyer a lot to gain in negotiations with a seller, and telephone is a better tool for doing trade. This leads to bilateral trade, outside the Nord Pool exchange. Today there is no way to negotiate when using the electronic commerce solution at Nord Pool. All offers are placed on the basis of “take it or leave it”.

A concluding remark is that large spread leads to telephonebased trade, small spread leads to use of electronic commerce.