A household survey conducted in 1986 as part of a study into the prevention of hot tap water burns found that 50 per cent of the immersion heater installations visited produced hot water at temperatures of 60 degrees C or greater. The Electricity Research and Development Centre has carried out a new detailed survey of over 200 electric immersion heater installations to ascertain the effectiveness of thermostats in controlling hot water temperatures. This survey found that immersion heater thermostats were effective and reliable devices, but it was disturbing to record the 71 per cent of the thermostats inspected were set at temperatures greater than 65 degrees C. Hot water temperature measurements showed that only 20 per cent of the homes had hot water with a temperature greater than 65 degrees C at the tap. One possible reason for this may have been the use of hot water by the residents before the temperature measurements were made because, while conducting the survey, it was not possible to have the immersion heater switched on in every apartment due to the time switching arrangements. For the age group surveyed, with an average age of 72 years, the provision of a device to indicate the remaining hot water in a storage cylinder was thought to be helpful but more than half the respondents indicated that they did not want new kinds of remote temperature control.(ABSTRACT TRUNCATED AT 250 WORDS)