What Are Energy Performance Indicators (EnPI) And Why Are They Important?

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energy performance indicator line graph

Energy Performance Indicators are a metric for tracking energy efficiency. They help to normalise energy consumption by any measurable, influencing factor. They are a commonly used tool by energy professionals, and a necessary requirement for ISO 50001 certification.  

For example, consider a factory making widgets. You can see the factory’s energy consumption, in kWh, on the plot below: 

energy consumption graph

The factory’s energy manager, who is responsible for ensuring a high level of efficiency, may be concerned over the spike in consumption from the 6/01 to the 08/01. 

The energy manager knows the factor affecting energy consumption the most is the number of widgets produced by the factory. This is added to the plot, as seen below. 

energy consumption vs widgets produced graph

This extra data adds insight, showing that the spike in consumption is likely caused by an increase in production. This relationship can be captured by a single metric, an Energy Performance Indicator (EnPI). This shows the amount of energy used to produce one widget (kWh per Unit), and is calculated as follows: 

Energy Performance Indicator = Energy Consumption Energy (kWh) ÷ Widgets Produced (# Units).

Plotting this indicator value over time gives us the following results…

energy performance indicator (EnPI) graph

We can see that the spike from the 6/01 to the 8/01 has completely disappeared, as the EnPI accounts for the increase in production. However, our attention is now brought to a spike from the 16/01 to the 18/01, which was not noticeable in previous graphs. This time, we can be sure this is not caused by an increase in production. 

To investigate these results further, we could look at adding extra influencing factors into the indicator, such as weather or degree days, building occupancy, and public holidays. This increase in complexity can provide further unique insight into the drivers behind energy efficiency.  

Energy performance indicators are used by leading energy professionals, providing a useful addition to the toolbox of anyone looking to improve their energy efficiency.  

These indicators form part of the requirements for achieving ISO 50001 certification. Factors included in the indicator must be relevant to the organisation, and demonstrate an improvement in energy efficiency. 

To learn more, or see how we use Energy Performance Indicators, get in touch at

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Angus Doherty
Angus Doherty

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