## 2 Related Work
There are some ongoing global projects aiming at coordinating actions such as the development of specifications and standards for energy saving. A relevant example is the ZigBee(r) Alliance [29], which produces innovative standards to enable manufacturers help customers with the deployment of the Internet of Things (IoT) through the establishment of Machine-to-Machine (M2M) wireless sensor and actuator networks. This allows the easy and cost-effective addition of intelligent new features that improve the efficiency, safety, security, reliability, and convenience of products and services. Some specific standards have been set for energy saving and energy efficiency: ZigBee Building Automation, ZigBee Smart Energy, ZigBee Home Automation or ZigBee Light Link. Emerging examples that include some of the tools mentioned above are smart cities [30], which have a new energy management model, achieving a significant reduction of CO\({}_{2}\) emissions. In this case, the use of energy storage systems with batteries is promoted, so that part of the available energy can be consumed afterwards for electric transportation, street lighting, or the air-conditioning of buildings. This kind of global actions may also comprehend complementary measures; e.g.,: the model used to enhance the demand response management of residential electricity consumers presented in [31], the use of models to improve the energy efficiency and usage in smart buildings, as proposed in [32; 33], the application for reducing costs and enhancing energy savings with smart grids in railway lines presented in [34], or the appearance of platforms for the energy data analysis and management described in [35]. Energy saving is a topic in which all concerned parties must collaborate. However, efforts should not only be directed to the efficient generation of energy or to obtaining a larger amount of energy from renewable sources. The optimal solution would only be obtained by also looking into the transportation and consumption of energy [36]. Some efforts have been put on the distribution grids, such as that shown in [37], which presents a new methodology for the smart metering, monitoring and analysis of the grid, using Power Line Communications (PLC), low-voltage feeders and phase identification of smart electric meters. To face the increment of the share of renewables in the energy mix, novel techniques are proposed in [38] to avoid destabilizing the grid by providing a fast response to possible overloads. But, for an adequate control of the electricity supply grid in these cases it is also necessary to act at the demand-side [39; 40; 41] by complementary smart grid developments; e.g., solutions providing a fast response that matches consumption to supply peaks or differing energy usage to off-peak consumption periods. Energy suppliers worldwide are beginning to implement new working policies and tools to contribute to energy saving through energy efficiency. Smart Meter Texas(tm) is a State of Texas (USA) utility that allows users to view their daily electricity usage, and to employ data to understand their consumption patterns. It provides users with the capability to manage their energy usage, and the opportunity to reduce their costs [42]. In Spain, a new active billing system for small consumers is being implemented. It consists of a variation in energy costs, according to the time at which energy is consumed, thanks to the installation of smart meters. Red Electrica de Espana [4], the company responsible for the operation of the Spanish electric system, provides data about energy generation and consumption in real time. Consequently, this information allows the creation of new software tools that provide users with new ways of managing their energy consumption. All these new developments are bound to cause a change in society, which is key to achieving a sustainable energy future.