Thermal plant bids and market clearing in an electricity pool. Minimization of costs vs. minimization of consumer payments

The Spanish wholesale electricity market started on January 1st 1998. Though it is based on simple price/quantity bids, it incorporates some provisions to take thermal plant running requirements into account. This paper presents these rules and its mathematical treatment, focusing on a possible implementation of the "minimum income condition", which allows thermal generators to declare minimum stable loads. It also shows another key point in the debate: whether the algorithm should minimize costs or consumer payments.