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Quantification of energy savings from Ireland’s Home Energy Saving scheme: an ex post billing analysis

Abstract

This paper quantifies the energy savings realised by a sample of participants in the Sustainable Energy Authority of Ireland’s Home Energy Saving (HES) residential retrofit scheme (currently branded as the Better Energy Homes scheme), through an ex post billing analysis. The billing data are used to evaluate: (1) the reduction in gas consumption of the sample between pre- (2008) and post- (2010) scheme participation when compared to the gas consumption of a control group, (2) an estimate of the shortfall when this result is compared to engineering-type ex ante savings estimates and (3) the degree to which these results may apply to the wider population. All dwellings in the study underwent energy efficiency improvements, including insulation upgrades (wall and/or roof), installation of high-efficiency boilers and/or improved heating controls, as part of the HES scheme. Metered gas use data for the 210 households were obtained from meter operators for a number of years preceding dwelling upgrades and for a post-intervention period of 1 year. Dwelling characteristics and some household behavioural data were obtained through a survey of the sample. The gas network operator provided anonymised data on gas usage for 640,000 customers collected over the same period as the HES sample. Dwelling type data provided with the population dataset enabled matching with the HES sample to increase the internal validity of the comparison between the control (matched population data) and the treatment (HES sample). Using a difference-in-difference methodology, the change in demand of the sample was compared with that of the matched population subset of gas-using customers in Ireland over the same time period. The mean reduction in gas demand as a result of energy efficiency upgrades for the HES sample is estimated as 21 % or 3,664 ± 603 kWh between 2008 and 2010. An ex ante estimate of average energy savings, based on engineering calculations (u value reductions and improved boiler efficiency and use through heating controls), suggests a technical reduction potential of 5,676 kWh per dwelling. Equating this with the gas reduction in the sample suggests a shortfall of approximately 36 ± 8 % between technical potential and measured savings. This shortfall includes the effects of direct and indirect rebound effects, variations in ex ante assumptions and achieved u values and efficiencies for upgraded dwellings. The profile of household characteristics in the HES sample is influenced by the self-selected nature of scheme participants. Self-selection bias and other possible biases in the sample data impact on the validity of the comparison. Data limitations for individual households across explanatory variables in the control and treatment groups precluded corrections for these biases in the sample; however, the profiles of separate comparable data sets were used where possible to quantify the differences in the explanatory variables and how these might impact on the measured energy saving with reference to the relevant effects identified in the literature.

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Notes

  1. 1.

    This scheme is administered by SEAI; since this study was undertaken, the scheme has been incorporated into the Better Energy Homes scheme (see http://www.seai.ie/grants/).

  2. 2.

    i.e. estimated energy savings obtained through the implementation of a specific energy efficiency improvement measure (in kilowatt-hours) are added to energy savings results from other specific energy efficiency improvement measures.

  3. 3.

    Bord Gáis Networks operates the GPRO function on behalf of Gaslink. ESB Networks operate the Meter Registration System Operator, with responsibility for the processing/aggregation of electricity meter data.

  4. 4.

    The GPRO is the administrative service that is established to support the competitive natural gas market and market opening process. Bord Gáis Networks operate the GPRO function on behalf of Gaslink. (www.gaslink.ie).

  5. 5.

    These members of society are addressed separately through the Better Energy Warmer Homes scheme designed specifically for this cohort http://www.seai.ie/Grants/Warmer_Homes_Scheme/.

  6. 6.

    An alternative might be that the BER was undertaken as required for future sale of the subject household.

  7. 7.

    defined in the recent smart meter trial as dwelling with less than 1,000 kWh per annum gas usage

  8. 8.

    See www.seai.ie/ber for more details.

  9. 9.

    See http://www.seai.ie/Your_Building/BER/BER_Assessors/Technical/DEAP/

  10. 10.

    2009 is not examined as some HES sample households had upgrades in 2009 while some others had not.

  11. 11.

    Based on over 260,000 BER ratings certified as on March 2012, reduced to existing gas customers and matched to the HES sample on the basis of house type (final n = 38,761).

  12. 12.

    Whilst it is recognised that this is not a statistically significant sample of the population, it is currently the best available comparator data.

  13. 13.

    Type of dwelling is found by Leahy and Lyons (2009) to have a significant impact on energy demand; however, since this comparison is between the matched sample based on house type, this variable is no longer relevant for the comparison.

  14. 14.

    All households with more than two persons were found to be using more energy compared to the reference two-person household.

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Correspondence to Jim Scheer.

Appendix

Appendix

Table 6 Efficiency upgrades undertaken in the sample
Table 7 Measure combinations
Table 8 Unitary savings estimates

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Scheer, J., Clancy, M. & Hógáin, S.N. Quantification of energy savings from Ireland’s Home Energy Saving scheme: an ex post billing analysis. Energy Efficiency 6, 35–48 (2013). https://doi.org/10.1007/s12053-012-9164-8

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Keywords

  • Energy efficiency
  • Billing analysis
  • Ex post
  • Insulation
  • Policy analysis
  • Energy Services Directive
  • Self-selection
  • HES
  • Ex ante
  • Energy savings
  • Household upgrades