Energy giant E.on has paid out £1.2 million to customers and a further £1.9 million to energy charities following discussions with the regulator Ofgem, after it failed to offer compensation when its agents missed appointments.

Under Ofgem's Guaranteed Standards, energy firms are required to meet certain standards of service, including keeping appointments when visiting customers' homes. If suppliers don't meet these standards then they must pay an agreed amount of compensation.

E.on reported to Ofgem in 2014 that it had failed to compensate customers after some 35,000 missed appointments between 2011 and 2015. As E.on volunteered the information, Ofgem said it would work with the firm to make improvements and agree on compensation instead of taking formal enforcement action.

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How the £3.1 million is being distributed

E.on has already paid out £1.2 million to 24,000 domestic and small business customers. These customers have already been written to and sent a cheque - they were paid £20 for a failed gas appointment and £22 for a failed electricity appointment.

There were some affected customers which E.on wasn't able to contact - for example, if they'd since moved home. On their behalf, E.on is set to pay a further £1.9 million to charity - this will include some going to help service personnel through National Energy Action's Help for Heroes scheme and the rest will go to Citizens Advice.

What to do if you think you missed out on compensation

Unfortunately E.on says that if you think you should have been compensated for a missed appointment between 2011 and 2015 and didn't receive a cheque by the end of August, you won't be eligible for a share of the £3.1 million.

However, as all energy suppliers should now automatically pay compensation for missed appointments, it's worth complaining anyway. You can contact E.on by phone, online or by post and if you're unhappy with the response you receive you can escalate your complaint to the Energy Ombudsman.

Before going to the ombudsman you have to get in touch with your supplier, and give it eight weeks to look into your complaint. If the eight weeks passes and you don't get a response, or you're not happy with the one you get, then you can escalate the complaint.

You can also complain using the free online tool Resolver*, which will help draft and manage your complaint and escalate it if necessary too.

What your rights are if your supplier misses an appointment

Since 2015 Ofgem's Guaranteed Standards have stated that if your supplier misses an appointment it should pay you £30 in compensation within 10 working days. If it misses the 10-day deadline, it'll have to pay you another £30 on top.

Your supplier should automatically pay compensation for a missed appointment - if it doesn't, get in touch with it and if you're unhappy with the way it handles your complaint you can escalate it to Resolver* who'll pass it on to the Energy Ombudsman if your supplier doesn't sort things out.

What Ofgem says

Ofgem chief executive Dermot Nolan said: "E.on fell well short of the high standards we expect for consumers when it missed appointments and then failed to compensate customers."

"It's crucial that suppliers provide their customers with a fast and effective service, and make amends when things go wrong."

What E.on says

A spokesperson said: "As part of the Guaranteed Standards, we make a payment to our customers when our representatives don’t arrive at a customer’s property for an appointment when we say they will. We also make a further payment to the customer if the initial payment is not made within 10 working days.

“We identified and updated Ofgem that we had not consistently made these payments ... between 2011 and December 2015 to some of our customers. To fix this we have written to customers who have been affected to say sorry, explain what has happened and to give them a cheque for the missing amounts."