Installing smart meters in every house in the UK will save consumers "only 2%" on their annual bills, a committee of MPs has warned.
The Public Accounts Committee (PAC) said that, on average, consumers will save just £26 a year.
MPs also warned that the technology could be out of date by the time the roll-out is complete.
The Department of Energy and Climate Change (DECC) said smart meters will lower bills and make switching easier.
Installing the meters - which begins in earnest next year - will cost £215 per household, or £10.6bn.
Customers will be charged an annual amount on their bills to cover the cost, peaking at £11 a year in 2017.
The £26 annual figure would be the net saving, after the installation costs have been taken into account.