Changes in energy demand from low-energy homes

To measure change in energy demand, a follow-up study was conducted in 20052007 of 36 low-energy UK dwellings that were originally monitored for hourly energy consumption between 1989 and 1991. All results were compared under standardized daily external winter conditions of 5C. Overall, no significant evidence of change over 1517 years was found in average gas consumption (67 kWh/day, with a 95% confidence interval (CI)=55, 79) and average electricity usage (14 kWh/day; 95% CI=11, 18). Dwellings were then classified into low, middle, and high groups according to energy usage in 1990. Gas usage of the high group at follow-up was 107 kWh/day (95% CI=89, 125) in 20052007, and was consistent with increased floor space, but electricity consumption increased by 72% to 24 kWh/day (95% CI=18, 30). The high group comprised dwellings that were both larger originally than in the other groups and they were more likely to have been extended. These results are broadly consistent with national statistics that show a distribution of household energy expenditure increasingly skewed towards those on highest incomes. Findings suggest that efficiency measures remain effective over the medium-term, but once implemented, little further improvement is made by occupants. Energy policy should focus on households with the highest consumption as this is where potential reductions are greatest and increases in gas and electricity usage are most are likely to occur.