An aggregator is a business entity enabling smooth cooperation between a System Operator (SO) and small customers to trade electric power. In this cooperation each market actor (aggregator, small customer, system operator) looks for its own economic incentives. In this paper, we consider an aggregator, who manages a portfolio of domestic heat pumps (HPs). The aggregator aims at maximizing its profit while trading energy and providing balancing power in wholesale markets. The paper develops a Mixed Integer Linear Program (MILP) for optimal coordinated bidding of HPs consumption power in competitive day-ahead and real-time markets. The model enables an aggregator to shift the consumption of HPs to hours with lower market prices, while respecting the comfort of involved houses. A case has been studied based on data from Dutch pilot built in the scope of FLEXCoop project. Day-ahead and balancing market prices have been obtained from TenneT.