Heating consumption measurement in electrically heated dwellings

Abstract

Comparisons between energy consumptions of dwellings heated by different fuels are often hampered by the lack of published, practical data. This paper provides an analysis of electric space heating measurements from a project carried out by the Building Services Research and Information Association (BSRIA), and from a separate study by the Building Research Energy Conservation Support Unit (BRECSU) funded by the Energy Efficiency Office. The analysis is based on data from 24 dwellings located in Scotland and Southern England from the BSRIA study and 17 dwellings located in the West Midlands from the BRECSU study. Heating systems comprised a mixture of storage and direct heaters. The consumption of on-peak and off-peak electricity was recorded on a fortnightly basis for a period of a year or more. Despite differences in tenure and system design, the results of the two studies are consistent. Based on these results the following conclusions can be drawn: the amount of electricity consumed at off-peak rates is primarily determined by the size and number of storage heaters installed and not by the design heat loss; for dwellings having electric storage heaters with charge capacities within 90-150% of the value recommended in the DOM 8 design guidelines, the percentage of electricity used at off-peak rates is at most 86%, and may be as low as 79% (taking the use of supplementary portable electric heaters into account); for dwellings which have heater capacities of 90% or less of the recommended values the average off-peak percentage is only between 49% and 69%; the measured electrical consumptions are consistent with levels expected for partial dwelling heating (e.g. when some rooms are heated for much less than nine hours a day). This suggests the proportion of consumption at off-peak rates for space heating established from this analysis are only appropriate for partial dwelling heating. The proportion of off-peak electricity required for whole dwelling heating is likely to be lower.