In the last post I set out a rough framework for organising various aspects of energy efficiency that impact on the energy costs of the energy that we use. Accessing any energy source requires the use of energy; and only a portion of the overall energy that we use goes directly to the specific service that we desire, such as moving goods or people from one place to another. In some situations—for example, many heating applications—almost all of the supplied energy is converted to directly useful forms, but all energy conversions entail energy costs of some magnitude Continue reading →