Measured energy demand of dwellings in Great Britain: The influence of physical, occupant and behavioural factors

The near universal approach to rating the energy efficiency of dwellings is to predict energy demand using standardised models, in the UK the Standard Assessment Procedure (SAP). Smart meter data offers the possibility of rating dwellings based on their actual, operational energy demand. A physical survey and household questionnaire enabled 148 dwelling, occupant, household and appliance characteristics to be derived for 2323 dwellings in Great Britain (GB). Using ordinary least squares and LASSO regression, the characteristics that explained the smart-metered energy demand were identified. Dwelling characteristics explained 36% of the variation in the weather-corrected, metered energy demand; the household and appliance characteristics explained a further 11%. The unexplained variability, 53%, is attribute to random inter-home variability. The dwelling’ s age, type and heating fuel, and the number of occupants and their energy saving behaviour, had a significant influence (p<0.01) on metered energy demand. In contrast, insulation levels and the way hot water was heated had a significant influence (p<0.01) on SAP-calculated energy demands, whereas the number of occupants, their appliance use and their behaviour had no influence at all. The SAP model thus misrepresents the factors that influence actual energy demand. It is concluded that smart-meter data can provide an operational rating for dwellings, and that this would substantially improve insight into the factors that influence dwelling energy demand. Importantly, it would correctly represent the importance of ergonomic design, guidance and policies aimed at influencing occupant behaviour as a route to reducing domestic energy demand.