LENI - Lighting Energy Numeric Indicator

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BS EN 15193 was developed to help support the European directive on the Energy Performance of Buildings (2002/91/EC.)4. It is one of a set of standards that cover all aspects of energy consumption in buildings.

Thestandard introduces theconcept of the Lighting Energy Numeric Indicator (LENI) which is used to express the total amount of energy used by a lighting systemper square meter, per year. 


The standard describe how the LENI value may be calculated or measured. There are two method of calculating LENI:

Quick Method

The quick calculation method makes a lot of simplifications and assumptions but the standard is set up so that for a given situation the quick method will nearly always result in a higher estimation of energy use.  To aid in the understanding and calculation of LENI we have provided an Excel spreadsheet that assists in the Quick Calculation method. E&OE

Comprehensive Method

Forthe comprehensive calculation it is necessary to apply formulae 6.2 and 6.3 doing a much more detailed analysis ofthe building in question to determine the factors used and if needed summing the results over different time periods.  The process is quite complex.  The calculation process is given in the European standard and it has been implemented in commonly available lighting software.


The metering method of determining the LENI value for a given installation involves measuring the total amount of energy used over the course of a year, from the lighting installation, dividing by the total area (m2) being illuminated.