Balancing energy demand and production is becoming a more and more challenging task for energy utilities. This is due to a number of different reasons among which the larger penetration of renewable energies which are more difficult to predict and the meagre availability of financial resources to upgrade the existing power grid. While the traditional solution is to dynamically adapt energy production to follow the time-varying demand, a new trend is to drive the demand itself by means of Direct Load Control (DLC). In this paper we consider a scenario where DLC functionalities are deployed at a large set of small deferrable energy loads, like appliances of residential users. The required additional intelligence and communication capabilities may be introduced through smart plugs, without the need to replace older " dumb " appliances. Smart plugs are inserted between the appliances plugs and the power sockets and directly connected to the Internet. An open software architecture allows to abstract the hardware sensors and actuators integrated in the plug and to easily program different load control applications.