Can you save money on off-peak electricity?

Are you on an Economy 10 energy tariff? Then you'll know that not all off-peak electricity deals are listed on price comparison websites. Find out whichenergy firms supply Economy 10 meters, so you can find the best deal.

Switching is simple if you have a regular energy meter, prepayment meter, or even an Economy 7 meter. You can put your details into an energy price comparison website to find a list of available tariffs.

But it's not so simple for around 700,000 homes that have'restricted' meters, including Economy 10 (E10) meters . Not all energy firms can accept customers on these meters, and the tariffs often aren't advertised online or listed on price comparison websites.

These customers overpay by around £154 per year, compared with customers on the cheapest single-rate tariff, according to the Competition and Market Authority's 2016 report.

Wecontacted 26 of the biggest energy firms to put together a list of E10 suppliers, so you'll know where to start if you're looking for a cheaper deal.

If you're not on Economy 10, compare gas and electricity priceswith Which? Switch, our independent switching service. Or you can call on 0800 410 1149 or 01259 220235.

Economy 10 suppliers

Economy 10 is a time-of-use electricity tariff. It offers 10 hours of cheaper electricity each day. It's similar to Economy 7 (which gives seven hours of cheaper electricity) and is usually linked with night storage heaters.

Typically, you'll get seven cheaper hours overnight, and another three in the afternoon, although exact times vary according to the region you live in.

We found seven energy firms thatoffer E10 tariffs to new customers*. They are:

• EDF Energy (except for customers in North East England)
• EonUpdate May 2017:Eon is no longer accepting customers with older E10 meters which have two MPANs. To join Eon, you must have a newer E10 meter with one MPAN. If you are already an Eon customer, it will upgrade your E10 meter free of charge.
• Good Energy
• Green Energy
• M&S Energy
• So Energy
• SSE

Ovocan also supply customers with E10 meters, using new smart meter technology, through a partnership with VCharge. Octopus Energy can accept customers and put them on an Economy 7 tariff but with 10 off-peak hours. British Gas told us it can accept customers with E10 meters, and offer them a 'best fit' Economy 7 tariff.

Prices vary by region. To find the best deal for you, call these firms directly to compare prices. But don'tswitch to a new firm until you've found out what its customers really think of it - we reveal thebest and worst energy firms.

*Research: April 2017.

The future of Economy 10

Customers with Economy 10 and other restricted meters face a 'lack of price transparency concerning the tariffs that are available to them', the Competition and Market Authority (CMA) found.

Eight in ten (79%) customers with these meters have never switched supplier. For some, changing supplier could involve replacing their meter (which could cost), and potentially rewiring their home.

But from September 2017, customers with restricted meters will be able to switch electricity tariff and supplier free of charge. Energy companies with more than 50,000 customers must make their single-rate tariffs (available to customers on standard meters) available to customers with Economy 10 and other meters, following remedies introduced by the CMA.

Energy companies will not be able to charge customers to have their restricted meters replaced so that they can access these tariffs. If you have a restricted electricity meter, your bills, renewal letter and other written communication will tell you that you can switch tariff or supplier.

If an energy supplier cannot supply a tariff immediately, it must apply it retrospectively.

Smart meters and time-of-use energy tariffs

Time-of-use tariffs, where you pay a different price for energy used at different times or days, will be available toall customers (not just those with E7, E10 or other restricted meters) once you have smart metersfitted in your home. Energy firms will be able to offer tariffs thatcharge different rates for peak or off-peak energy use. These may help encourage people to use electricity at times when there's less demand.

British Gas and Green Energy UK have already launched time-of-use tariffs for customers with smart meters. British Gas's HomeEnergy gives customers free electricity on either Saturday or Sunday. Green Energy's Tide offers seven hours of cheaper electricity between 11pm and 6am.