**Preface to "Environmental and Energy Efficiency Evaluation Based on Data Envelopment Analysis (DEA)"**

Most countries have increased their energy generation and use based on fossil fuels, whose low prices have facilitated economic development and the well-being of society. However, fossil fuels, largely responsible for climate change, must give way to cleaner energies and thus avoid the technological gap between developed and developing countries.

The measurement of energy efficiency is a key issue to orient the development of these new energy sources that have to propitiate the change in the production and consumption models. Energy efficiency also has to enhance the preservation and repair of the current environment, so that the negative effects that the consumption of fossil fuels have on people's health are also eliminated.

To measure energy efficiency, data envelopment analysis models are relevant tools where inputs, desirable outputs and undesirable outputs are jointly considered, providing a holistic approach. In this context, the articles published in this Special Issue are a first step to develop new investigations that allow us to better understand the impact of climate change on the environment.

> **Ramon Sala-Garrido, Mar´ıa Molinos-Senante** *Editors*
