Final answer:
Efficiency indicates the effectiveness of energy use and is key for judging sustainability of energy sources. Energy intensity informs us about energy consumption relative to economic output.
Step-by-step explanation:
Efficiency is a description of the relative amount of resources used in obtaining effectiveness. It is a measure of how the input of energy is converted into work or useful energy. The term is often used in the context of energy consumption, where a lower energy intensity indicates a reduced amount of energy consumption for a certain economic output, allowing for higher economic output with the same rate of energy consumption.
In the field of sustainable development and resource management, efficiency is crucial for judging the sustainability of various energy sources. For instance, spending money on an airplane trip is far more energy intense than spending the same amount of money on legal advice, suggesting the former is less efficient in terms of energy usage. Creating a matrix of energy source properties, as discussed in the provided reference material, helps to identify the relative strengths and weaknesses of different energy sources at a glance. This quantitative assessment is essential for making informed decisions about energy use and can lead to strategies for adapting to reduced resource availability, aiming to maintain a satisfying lifestyle in a resource-constrained world.