Developing regulation of energy efficiency of private sector housing (REEPS): modelling improvements to the target stock - Research Summary

This Research Summary presents the main findings from the 2014-15 research project into improving the energy efficiency of the private sector dwelling stock in Scotland, undertaken by Ipsos MORI and Alembic Research. The research identified the least cost methods of improving the target stock, namely those dwellings falling into Bandings E, F and G on the SAP rating scale.


In terms of overall savings in relation to fuel costs, CO2e emissions and Primary and Delivered Energy consumption, Scenario 1 has the smallest impact and Scenario 3 has the largest impact due to the difference in terms of number of dwellings improved and scale of the improvements required. Generally, however, the more efficient a dwelling is pre-improvement measures, the smaller the impact of the improvements will be.

With regard to annual fuel cost savings of the different scenarios:

  • Scenario 1 would give an annual fuel cost savings of £16.1 million
  • Scenario 2, £79.0 million
  • Scenario 3, £193 million
  • Scenario 4, £111.6 million

The average impact per dwelling differs by the scale of the improvement required and the base position of the dwelling. For the least efficient dwellings, the capital cost of improvements is lowest, and the financial gains are highest. It follows that the payback period is the shortest for these dwellings. Scenario 1 has a mean payback period of 1.2 years, compared with 2.7 for Scenario 2, 5.5 for Scenario 3, and 3.5 year for Scenario 4.

Impact on CO2e emissions were estimated:

  • Scenario 1 would give annual savings of 62,700 tonnes,
  • Scenario 2 amounts to 361,700 tonnes,
  • Scenario 3 amounts to 1.05 million tonnes,
  • Scenario 4 amounts to 606,000 tonnes.

The larger the scale of the improvement measure the greater the reduction in CO2e emissions. However the level of efficiency prior to improvements does not impact CO2e emissions savings.

Impact on delivered and primary energy savings were estimated to be:

  • Scenario 1 would lead to an annual saving of 204m kWh per annum for delivered energy and 306m kWh for primary energy.
  • Scenario 2 leads to an annual saving of 1273m kWh for delivered energy and 1689m kWh for primary energy.
  • Scenario 3 leads to an annual saving of 3569m kWh for delivered energy and 5030m kWh for primary energy.
  • Scenario 4 leads to a savings of 2,044m kWh for delivered energy and 2968m kWh for primary energy.

As with energy costs, the larger the scale of improvement made, the greater the impact. Further improving a dwelling by one band has a larger impact on the least efficient dwellings.

This document, along with the full Research Report and modelling results for 355 archetype dwellings is available at Further information about social and policy research commissioned and published on behalf of the Scottish Government, can be viewed at: If you have any further queries about social research, please contact us at or on 0131-244 2111.


Email: Silvia Palombi

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