Installing smart meters may not result in households saving energy, a study has suggested.
Smart meters had been considered as one component in an infrastructure to help use energy more effectively, and cut bills and emissions.
Research by a University of Oxford scientist found that the devices alone were unlikely to lead to an overall reduction in the demand for energy.
The findings appear in the journal Building Research and Information.
"A lot of us are using gas and electricity without realising we are using it," explained author Sarah Darby from the university's Environmental Change Institute (ECI).
"If you had a wood fire and went away for the weekend, then the fire would go out. However, if you leave the central heating or electrical appliances on when you go away, you may be none the wiser."
It is why, Dr Darby added, the "feedback effect" (which tells people how much energy was used over a period of time, or how much energy a particular activity/appliance consumed) in energy demand reduction was so important.
"Helping people who wanted to save energy use the information they could get from their metering and bills was an important part of that feedback," she told BBC News.
"Using the old-style meter means that you have got to be fairly diligent to do that - even if you do check it every day or month, it does not give you a breakdown of how you are using the gas or electricity."