Coyne et al. analyse the energy savings made by a government programme in Ireland designed to reduce energy consumption in social housing though the installation of efficiency measures, such as replacement boilers, double glazing and cavity wall insulation.

They find that predicted savings, based on commonly used engineering models overestimate energy savings made. In the sample of Irish social housing stock studied, energy savings were found to be 50% lower than predicted. The authors suggest that tenants may reduce the saving made by using more energy to keep their homes warmer, causing this ‘rebound effect’.

12% of the UK’s carbon emissions originate from homes. Most of that energy use (65%) is for heating living spaces. Residential emissions, particularly from heating, need to be cut for the UK to meet emission reduction targets. In the short term energy savings can be made by increasing energy efficiency in heating systems. In the long term a reduction in fossil fuel use is necessary.

The researchers highlight the importance of evaluating the impact of energy efficiency improvements and policies to reduce energy consumption, by using ex-post, observed data rather than depending on modelled predictions.

Key points for decision makers

  • 12% of the UK’s emissions are from the residential sector and 65% of energy use in homes is for heating living spaces.
  • To meet the UK’s fifth carbon budget and reduce emissions by 57% compared to pre-1990 levels by 2030, emissions from home heating will need to decrease substantially.
  • The UK’s Clean Growth Plan (due to be published this year) is expected to feature plans for increasing residential energy efficiency.
  • This research finds that energy efficiency installation programmes administered by the Irish Government have successfully reduced energy consumption in targeted households
  • However, models used to predict energy savings (such as SAP in the UK and DEAP in Ireland) are found to overestimate. Real energy savings are 50% lower than predicted in this housing sample.
  • The authors hypothesise that the shortfall in energy savings could be due to a ‘rebound effect’.
  • Energy efficient homes require less energy to heat, this reduces the cost of keeping the home warm. Households in the study may have taken back part of the energy saving predicted by heating their homes to a warmer temperature which might not have been affordable prior to energy efficiency installations.
  • The authors suggest that policy-makers should use actual energy consumption data rather than relying only on data predicted by engineering models, based on standardised assumptions for occupancy and behaviour when evaluating energy savings from energy efficiency policies.
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