Expected Energy Not Served (EENS)
'Expected Energy Not Served' (EENS) or 'Expected Energy Unserved' (EEU) represents a metric which could be used to measure security of supply as well as to set a reliability standard in the electricity market.
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2 October 2020
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This is the amount of electricity demand - measured in MWh – that is expected not to be met by generation in a given year. This combines both the likelihood and the potential size of any shortfall.
Just as in the case of LOLE, the EENS should not be taken to mean there will be that particular amount of blackouts, because in the vast majority of cases, this would be managed without significant impacts on consumers (DECC Reliability Standard Methodology, July 2013).
The so-called 'Winter Energy Package' applies the EENS as the key metric for European resource adequacy assessments.
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The said estimations cover the overall adequacy of the electricity system to supply current and projected demands for electricity.
Article 19(4)(h) and Article 19(5)(c) of the Proposal for a Regulation of the European Parliament and of the Council on the internal market for electricity (recast) of 30 November 2016 (COM(2016) 861 final 2016/0379 (COD)), required the use of EENS (and LOLE) as reliability standard indicators (the rule implemented in Article 25(3) of the final Regulation (EU) 2019/943 of the European Parliament and of the Council of 5 June 2019 on the internal market for electricity (recast)).
According to Article 23(5)(j) of the said Regulation (EU) 2019/943, the European Resource Adequacy Assessment (ERAA), carried out by the ENTSO for Electricity on an annual basis, is to be based on a transparent methodology, which must include, among other indicators, also the EENS.
According to the Methodology for calculating the value of lost load, the cost of new entry and the reliability standard in accordance with Article 23(6) of Regulation (EU) 2019/943 of the European Parliament and of the Council of 5 June 2019 on the internal market for electricity (Annex I to the ACER Decision No 23/2020 of 2 October 2020 on the Methodology for calculating the value of lost load, the cost of new entry, and the reliability standard (VOL CONE RS)) ‘expected energy not served’ (EENS) means expected ENS; while ‘energy not served’ (ENS) is, for a given geographic area and time period, ‘the energy which is not supplied due to insufficient capacity resources to meet the demand’.