More than half of energy customers with a smart meter have found the devices stopped working when they switched supplier, research suggests.
Which? found that almost six in 10 of those surveyed (58%) found either their smart meter, their in-home display or both stopped working when they moved to a new energy company.
More than 13.5 million smart meters have been installed in the UK and a quarter of homes have had one of the devices fitted.
The vast majority of these are first-generation SMETS1 meters while 300,000 more advanced second-generation SMETS2 devices have been installed.
SMETS1 meters can go “dumb” when a customer switches, meaning they stop sending automatic meter readings, or the in-home display showing energy usage in pounds and pence stops working properly.
The watchdog’s poll suggests just 42% of energy customers who have tried to change supplier after getting a smart meter were able to switch without any problems.
A third of people (32%) who switched after getting a smart meter said their new supplier replaced their smart meter.
However, Which? said it had received reports of customers whose replacement device also stopped working.
Energy customers have been advised for years that the most effective way to ensure they are on the best deal for their gas and electricity supply is to switch.
Which? found that a third (34%) of people said their energy consumption had gone down since getting a smart meter. However, one in five thought that their usage had increased since having a device fitted.
It noted that “many” customers were positive about smart meters, with 72% of those with a device rating their supplier as good or excellent at helping them understand and reduce their energy use compared with just over three in five (63%) of those who do not have one.
Which? chief customer officer Sarah Threadgould said: “Consumers need reassurance that the smart meter roll-out will bring greater convenience and a fairer energy market – not just hassle and soaring costs funded by their bills.
“The Government needs to outline clear solutions for millions of people stuck with smart meters that risk cutting them out of the benefits of being able to monitor their energy use and use this information to switch to a better deal.
“For now, our advice is for energy customers with a first-generation meter not to be discouraged from switching, as they could still save money, despite the risk of their meter going ‘dumb’.”
Robert Cheesewright of Smart Energy GB, the national campaign for the smart meter roll-out, said: “We share the frustrations of consumers when it comes to losing their smart service, but we are well on the way to solving those issues.
“The first-generation end date is just a week away (March 15) and over half a million second-generation meters have been installed, putting us a step nearer to a greener and more affordable energy system.”
A Department for Business, Energy and Industrial Strategy spokeswoman said: “The upgrade to the national smart metering network to support the enrolment of first generation smart meters has started and will be completed by the end of 2020 to ensure all devices stay smart when switching.
“Around 90% of smart meters installed continue to operate in smart mode and those which have temporarily lost smart functionality will be prioritised for enrolment into the network.”
Which? surveyed 2,910 members of the public who have smart meters online in September.