The cheapest deals available from the big six providers – British Gas, EDF Energy, E.ON, Scottish Power, npower and SSE – all have smart meter clauses attached, according to autoswitching service Migrate.

These clauses range from mandatory smart meter installation within a set time period to agreeing to be contacted about smart meter installation.

Smart meters are devices that automatically send meter readings to your supplier. They also allow customers to monitor their own energy use.

The government says smart meters will cut customers’ bills as they eliminate estimate readings.

However, many households have reported technical issues with their devices such as displays not working, devices ceasing to function entirely and first generation meters (SMETS1) losing smart functionality when switching provider.

Originally, suppliers had until 2020 to offer all customers a smart meter. This deadline was recently extended to 2024, by which time at least 85 per cent of all customers must have a smart meter installed.

Smart meters are not compulsory but there have been reports of suppliers using bullying tactics to meet their targets, including telling people they are a legal requirement.

The findings from Migrate show the cheapest tariff from British Gas costs on average £949 per year. But customers will have to book a smart meter installation appointment within three months.

This tariff would save the typical customer on a standard variable rate £230 a year.

The cheapest E.ON deal is £938 but this comes with the condition that you will be contacted about a smart meter installation. This deal is £241 cheaper than E.ON’s standard tariff.

Npower’s best tariff costs £1,134 on average a year but you need to have a smart meter or agree to have one installed to qualify for the rate.

Scottish Power and SSE also make customers sign up for a smart meter or discuss installation if they want the best deals.

EDF Energy is the only big six supplier that offers customers an opt out.

George Chalmers, chief executive of Migrate, said: “The smart meter roll-out has been nothing short of a car crash, filled with high pressure sales tactics and confusion about meter benefits.

“Worse still, those who don’t comply with their supplier could risk being locked out of the best deals, effectively blackmailing customers into taking a smart meter that might not work when they come to switch.

“If cheaper tariffs continue to be promoted to those that either have or are willing to have a smart meter installed in their home, then there’s a real risk that those who choose not to opt-in could be left out in the cold.”