Vincent BRYANT

By the way, what’s Energy Efficiency?

Vincent BRYANT

Vincent BRYANT

Speaking about Energy Efficiency with everybody, you may have noticed that almost everyone has her own definition of the topic. For some of us, Renewable Energies (REn) are part of Energy Efficiency such as solar panels or green district heating. For others, only actions on active systems or building’s envelops are eligible to this so-called appellation.

What’s the truth amongst all these potential definitions? Is there really a unique definition? Does it make sense to think in terms of an overall spectrum? What if there were several relevant definitions of Energy Efficiency, each one suitable for a given context?

Let’s delve into this.

According to World Energy Organisation, and from a very practical approach,

Energy efficiency improvements refer to a reduction in the energy used for a given service (heating, lighting, etc.) or level of activity.

This definition raises some questions: how to define a reduction? Is a reduction always predictable and measurable? How can we describe the level of activity? Are levels of activity consistent through the time? According to Wikipedia, the definition is more technical and less broad with less combinations.

Energy conversion efficiency (η) is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.

Here again, we could challenge the absolute relevance of this definition and find non satisfactory examples. Let’s have a look at International Energy Agency. This time the definition is very large, even almost macro-economical.

Energy efficiency is a way of managing and restraining the growth in energy consumption. 

Finally, we could keep playing this longstanding game.

My truth is: there are several relevant Energy Efficiency definitions. But not all of them can suit every contexts. I suggest the following non-exhaustive and fairly improvable cases:

  • Marketing context: “Energy Efficiency is for a same need, a same level of comfort, a same usage, less consuming, better consuming, less polluting”
  • Technical context: “Energy Efficiency is, ceteris paribus, the performance obtained on a given system (equipment, building, and so on) between the primary energy used and a tangible measurable level of service”
  • Popularized context: “Energy Efficiency is all the actions that lead to save energy”
  • Lobbying context: “Energy Efficiency stands for all the available needs to reduce significantly primary energy consumption for a given level of consumption”

Happy to debate on that… 🙂

Soon, we’ll see the practical difference between Energy Efficiency and Energy Effectiveness, and the way we can use it to sell Energy Efficiency solutions more easily to clients.


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