We had a smart meter installed by Octopus... the cost of making a cuppa went from 1p to £5 overnight

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Boiling the kettle for a cup of tea sent Ford and Ann Jones into a panic when their newly installed smart meter showed it adding £5 to their electricity bill. 

To make sure their eyes were not deceiving them, they tried the washing machine – and found they were being charged £15 to clean their clothes. 

They rang their utility company Octopus Energy to try to find out why their bills had suddenly rocketed following the installation of a smart meter a few weeks earlier. 

Before then, boiling a kettle would add only about a penny to their bill. Initially, the energy supplier ignored their pleas. 

It was only when they contacted an independent engineer who had fixed solar panels to their roof that he spotted a 'CT clamp' had been reconnected the wrong way round, causing the meter readings to go 'haywire'. 

Experts believe this is far from an isolated incident. One electrician says he was called out a dozen times last year due to smart meter installers re-wiring existing solar panel connections the wrong way round. 

Not so smart: The meter was installed incorrectly - and pleas from the couple were ignored

This CT clamp is a 'current transformer' half the size of a matchbox that fits over energy wires coming into a smart meter and measures electricity going in and out. 

Sometimes they come with arrows printed on the clamp – but these are hard for anyone but an electrician to read. 

In numerous phone calls from when their smart meter was installed last February, the retired couple in their 70s were told to 'ignore the meter' and that the 'meter might take a few weeks to settle down'. 

That was despite being charged £3,000 over a three-month period – more than ten times their usual quarterly bill. 

Ford says: 'Octopus told us not to worry – but that did not stop them still sending much higher bills.' 

The couple had downsized to their modest three-bedroom bungalow two years ago and installed a dozen solar panels on their south-facing roof in a bid to future-proof themselves against rising energy bills. 

Octopus Energy had claimed that a smart meter installed last February would keep tabs on their energy usage – and hopefully help keep costs down by showing them how to save electricity. 

Ford adds: 'Only after I logged on to Octopus's website and showed proof our energy usage had shot up once the meter was installed did they finally pay attention. 

'But it was not until August that we managed to get an engineer out to fix the problem. 

'I insisted on Octopus fixing the CT clamp because if I got another engineer out to do the work, the energy supplier could have said it was not their fault.' 

Octopus: The energy giant said it was a 'very rare error'

And Dave Cookman, a professional electrician with more than 20 years of experience on electrical installations – including solar panels – believes their experience is far from unusual. 

Dave, owner of D Cookman Electrical in Dunstable, Bedfordshire, says: 'This problem with people installing smart meters when they already have solar panels is becoming increasingly common. I have dealt with a dozen similar cases in the last year alone.

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'These clamps measure the flow of electricity using magnets. 

'Put the clamp back the wrong way round, which often happens with smart meters put in by people not skilled at handling the technology, and the reader will suddenly not have a clue what is going on – and might start telling you anything other than your real usage.' 

He adds: 'Energy suppliers such as Octopus are understandably not keen to admit responsibility. 

'My advice is to contact your installer immediately and insist they come out to fix the problem if energy bills unexpectedly rocket after you have agreed to have a smart meter fitted at home.' 

The couple were paid compensation by Octopus after Money Mail intervened and admitted that the engineer did re-install their CT clamp the wrong way around. 

Octopus said: 'We fit thousands of these clamps a year, and it's a very rare error, which meant some of our team didn't pick it up as quickly as we'd like.' 

If you have been affected by wild smart meter readings: toby.walne@dailymail.co.uk