We calculate savings using an organisation-level Energy Performance Indicator, showing how efficiently your organisation is using energy.
Determining energy savings involves analysing changes in parameters that are directly related to energy use. The methodology used in the M&R system calculates savings on a top-down basis for each organisation. This is done using an organisation-level Energy Performance Indicator (EnPI).
EnPIs enable organisations to determine how efficiently they are using energy as it accounts for changes in the activity level related to the energy use - or activity metric - of the organisation.
Calculating energy savings
A good EnPI demonstrates a clear link between energy use and the activities that directly influence consumption. This enables you to determine how efficiently your organisation is using energy because it accounts for changes in the activity metric of your organisation.
Each year, an EnPI is calculated by dividing the organisation’s total energy consumption, expressed as the total primary energy requirement (TPER), by the organisation-level activity metric:
Calculating energy saving since baseline
An organisation’s energy saving (%) since its baseline is calculated as the change in the EnPI since the baseline divided by the baseline EnPI value. For example, the energy savings made between the baseline and year 201X are calculated as follows:
This methodology accounts for an organisation’s energy performance as well as its energy consumption. Energy performance relates energy use to the service or activity level of the organisation.
The % saving is the key result published by SEAI for each organisation each year. A positive value indicates an improvement in performance (i.e. energy savings) since baseline, while a negative value indicates a deterioration in energy performance.
Tracking savings for local authorities
From an M&R perspective, local authorities have been considered to operate without water services since January 2014. Savings or deteriorations in performance made by local authorities while water services were within their scope (i.e. up to 2013) are ‘locked in’ and retained by the local authorities. This historical performance contributes to the local authorities' progress towards the 2020 target.
2013 is an important transition year in the calculations to track each local authority’s energy performance before and after the transfer of assets. The energy saving as of the end of 2013 is a particularly important value used in the calculations and it remains unchanged despite adjustments to consumption, activity metrics and EnPIs.
Local authorities can use one activity metric for the period up to and including 2013, and a different one from 2014 onwards. This enables them to track their energy performance before and after the transition of water services to Irish Water.
If your local authority is using different metrics for the two periods, your energy performance is calculated using:
- one EnPI based on the first metric for the period up to and including 2013
- a second EnPI (based on the second metric) from 2014 onwards
Your percentage saving since baseline as of the end of 2013 (calculated on the basis of your first EnPI) is combined with your percentage saving since 2013 (calculated on the basis of your second EnPI) to determine your overall saving:
Tracking savings beyond 2020
The methodology for tracking energy savings beyond 2020 has yet to be determined.
Another way to illustrate your organisation’s progress is using a normalised EnPI. This involves setting your normalised EnPI value in the baseline period to 100, and quantifying progress since then as movement from this 100 level.
The normalised EnPI is calculated as follows (for year 201X):
Advantages of normalised EnPIs
Normalised EnPIs are useful for publication as they are relatively easily understood to persons outside the organisation, and actual energy consumption cannot be derived from them.
They also facilitate some comparison between organisations. However, such comparisons should be made with care. Comparing two organisations’ normalised EnPIs is akin to comparing the percentage change in height of two different children over a year. The percentages don’t tell you how tall (energy efficient) the children (organisations) were at the beginning of the year or the number of centimetres grown (kWh saved) over the year. What they do tell you is how the two children (organisations) have performed ‘against themselves’.