This article describes a proposal for the participation of supercomputing platforms and datacenters in the electric market, by implementing demand response techniques and ancillary services. Supercomputing and datacenters are appropriate candidates to adjust their power consumption in order to help the electric network to fulfill specific goals, either by consuming available surplus of energy to execute complex tasks, or by deferring activities when energy is more expensive or generation is lower than normal. Their thermal/cooling infrastructures demand about half of the energy consumption and provide a large inertia that can be carefully used to interact with the power grid. These strategies allow implementing a smart management of the electric grid, achieving a rational utilization of renewable energy sources, and the correct utilization of information technologies to improve decision-making processes. A specific case study is presented: The National Supercomputing Center in Uruguay (Cluster-UY), for which strategies for optimal planning of the execution of tasks and energy utilization are proposed, taking into account the energy consumption, the Quality of Service provided to the users, and the thermal/cooling demands of the infrastructure. In addition, the business opportunities and business models for supercomputing and datacenters in the electric market are revisited. Results suggest the effectiveness of the proposed strategies to implement demand response techniques and provide ancillary services under the smart grid paradigm.