Co-op Energy is offering all existing customers including those with the GB Energy brand a "loyalty reward" of up to £150 until 31 July to stay with the firm and switch to its two or three-year fixed deals – but many are likely to save more switching to another supplier.

The bonus has been heavily promoted to customers coming to the end of a fix, particularly those on the super-cheap rates offered by GB Energy which end over the next few months. Co-op Energy took on GB Energy's 160,000 customers and kept the brand after the supplier went bust last November.

At the time, Co-op Energy agreed to honour all existing GB Energy fixed tariffs. But with these now set to end, it's offering all its dual-fuel customers – not just GB Energy customers – £150 to tempt them to stay and sign up to a new fix. Single-fuel customers can get £75.

We've crunched the numbers though, and if you're willing to switch supplier, it's likely you can find cheaper two or three-year deals elsewhere, even with the bonus factored in. And if you're just after the cheapest rate, those on typical use can save an average £140/year more moving to the market's cheapest one-year fix.

As prices vary by usage and region, it's always best to do a full market comparison using our free Cheap Energy Club – just factor in the loyalty bonus when comparing Co-op Energy deals.

How can I get the loyalty bonus?

To get it, you'll need to be an existing Co-op Energy or GB Energy customer, and you'll have to switch to one of the following tariffs by Monday 31 July:

  • Co-op Price Protect July 2019 – or GB Energy's version of this tariff, GB Price Protect July 2019
  • Co-op Price Protect July 2020 or GB Price Protect July 2020

But crucially, if you're currently locked into a Co-op Energy or GB Energy fix, you'll most likely be charged exit fees – typically £30/fuel – to move to one of these new fixes, which will cancel out much of the bonus. So this is really targeted at those who are on a Co-op Energy/GB Energy variable tariff, or within the last 49 days of their current fix.

Under rules from regulator Ofgem, any energy customer with less than 49 days to go on their fix is free to switch to another tariff, including with another supplier, without paying exit fees.

You won't get the bonus straightaway – you need to stick with the firm for at least a year. It'll be credited to your Co-op Energy or GB Energy account within 30 days of the first anniversary of you moving onto one of these tariffs, so you're unlikely to see it until at least August 2018. You could switch as soon as you get the bonus, but if you do you'll have to pay exit fees of £30/fuel.

Is the loyalty bonus worth it?

The Co-op and GB Price Protect July 2019 tariff costs a typical dual-fuel user an average £1,050/yr, while the July 2020 tariff costs an average £1,098/yr.

Then you've got the £150 bonus. Spread that across the length of the fix and the price of the two-year fix drops to £975 per year, while the three-year falls to £1,048 per year.

As this table shows, those two and three-year fixes are some way off the cheapest on the market, and an average £140/yr more than the market's cheapest tariff currently, from Iresa.

So if you're tempted by the Co-op Energy bonus, make sure you do a full comparison before signing up. As prices vary by usage and region it's possible it could work out cheapest for you. But it's likely many will be better off going with another supplier.

Average annual cost – dual fuel(i)

Provider – tariff Length of fix Price/year Exit fees
Co-op/GB Energy – Price Protect Jul 2019 Until 31 Jul 2019 £975 (incl £150 over 2yrs) £30/fuel
Flow Energy – MSM Fixed Sep 2019 (ii) Until 31 Aug 2019 £895 £20/fuel
Engie – Fixed Sep 19 v3 Until 30 Sep 2019 £898 £30/fuel
Co-op/GB Energy – Price Protect Jul 2020 Until 31 Jul 2020 £1,048 (incl £150 over 3yrs) £30/fuel
Engie – Control 3 years £1,000 None
Extra Energy – Clear Fixed Price Sep 2020 v1 Until 30 Sep 2020 £1,034 £30/fuel
Market's cheapest: Iresa – Flex4 12-month Fixed 1 year £834 None
Avg big-six standard variable tariff n/a £1,138 n/a
(i) This table is based on Ofgem typical usage figures. (ii) Only available via MoneySavingExpert and MoneySupermarket.