[50] Conservation is a personal choice

Energy efficiency is an input-output concept. It means ‘doing more with less’ and cannot be argued with. It’s good business sense and produces multiple benefits beyond a financial return [72, 77].

Energy conservation is a much more severe requirement and it requires ‘doing less’. This often involves trade-offs – flying less affects business or family relations. Absolute reductions in energy use could affect business productivity or citizens’ health and well-being.

It is risky to take the concept of reducing energy consumption too far. It can be safely applied to the technical performance of products or subsystems. It should not curtail necessary activities in projects, buildings or cities.