Jenny Crawley, Phillip Biddulph, Paul Northrop, Jez Wingfield, Tadj Oreszczyn and Cliff Elwell
Domestic Energy Performance Certificates (EPCs) are used in the UK to provide energy efficiency ratings for use in policy and investment decisions on individual dwellings and at a stock level. There is evidence that the process of creating an EPC introduces measurement error such that repeat assessments of the same property give different ratings, compromising their reliability. This study presents a novel error analysis to estimate the size of this effect, using repeated EPC assessments of 1.6 million existing dwellings in England and Wales. A statistical model of how measurement error contributes to variation between repeated measurements is set out, and exploratory data analysis is used to decide how to apply this model to the available data. The results predict that the one standard deviation measurement error decreases with EPC rating, from around ± 8.0 EPC points on a rating of 35 to ±2.4 on a rating of 85. This predicted error is higher than the limit recommended in UK guidance except in very efficient buildings; it can also result in dwellings being rated in the wrong EPC band, for example it was estimated that 24% of band D homes are rated as band C.
Crawley, J., Biddulph, P., Northrop, P.J., Wingfield, J., Oreszczyn, T. and Elwell, C. 2019. Quantifying the measurement error on England and Wales EPC ratings. Energies, 12: 3523. doi: 10.3390/en12183523Opens in a new tab
Banner photo credit: Alireza Attari on Unsplash