How to Write a Complaint Letter to the Energy Ombudsman UK: A Complete Guide
Your energy supplier has had eight weeks to resolve your complaint. Or they have sent you a deadlock letter saying they cannot help further. Either way, the next step is the Energy Ombudsman, and it is one most people either do not know about or do not use because they are not sure how.
The Energy Ombudsman is a free, independent service that can investigate your complaint, make a binding decision and order your supplier to pay compensation of up to £10,000, correct billing errors, apologise formally and take specific remedial action. Its decisions are binding on the supplier. Unlike a complaint to the supplier’s customer service team, you cannot simply be fobbed off.
This guide explains who can use the Energy Ombudsman, when you can go to them, what kinds of complaint they cover, how to write the complaint letter that gives your case the best chance, and what happens after you submit.
Who Can Use the Energy Ombudsman
The Energy Ombudsman is available to domestic consumers in Great Britain, meaning anyone who uses gas or electricity at their home. Since December 2024, the service was significantly expanded to also cover small and microbusiness consumers meeting revised eligibility criteria. From April 2025, it was further extended to cover disputes about heat network suppliers, meaning consumers who receive heat or hot water through a communal network rather than a gas boiler can now bring disputes about billing, customer service, installation, and loss of heat or hot water.
The service is entirely free to consumers. You do not need a solicitor, a claims management company or any professional help to use it. If you receive an approach from a company offering to manage your Energy Ombudsman claim for a fee or a percentage of any compensation, you do not need them. The process is designed to be used directly.
When You Can Go to the Energy Ombudsman: The Two Triggers
You can submit your complaint to the Energy Ombudsman once one of two things has happened:
Eight weeks have passed since you first formally complained to your supplier without resolution. The eight-week clock runs from the date you first raised a formal complaint with your supplier. It does not run from the date you called their customer service line for general help. You must have made a complaint, used the word ‘complaint’, and the eight weeks must have passed without the supplier resolving it to your satisfaction.
You have received a deadlock letter. A deadlock letter is a formal written statement from your supplier saying they have done everything they intend to do and cannot resolve the complaint further. If you receive one, you can go straight to the Energy Ombudsman regardless of how long the complaint has been running.
There is also a time limit on the other side: you must submit your complaint to the Energy Ombudsman within 12 months of receiving the supplier’s final response or deadlock letter. If you are approaching this deadline, submit your complaint immediately even if you do not yet have all your evidence together. You can add further information after submission.
What the Energy Ombudsman Can Investigate
The Energy Ombudsman covers the full range of disputes between domestic and eligible business consumers and their energy suppliers. The most common complaint types include:
Billing errors: Overcharging, incorrect meter readings used for billing, estimated bills that bear no relation to actual usage, bills issued for the wrong property or the wrong period.
Back-billing disputes: Under Ofgem’s back-billing rules, suppliers cannot charge domestic consumers for energy used more than 12 months ago if the error was the supplier’s fault. If your supplier has sent you a bill covering an older period, this is a specific and well-established complaint ground.
Switching problems: Issues arising when switching supplier, including final bills that are disputed, exit fees applied incorrectly, or credit balances not refunded after switching.
Credit balance refunds: Suppliers must refund credit balances promptly on request. Refusal or unreasonable delay is a complaint ground.
Poor customer service: Including failure to respond to complaints, misleading information given by customer service agents, and failure to follow Ofgem’s complaint handling rules.
Smart meter disputes: Including problems with smart meter installation, incorrect readings transmitted, or loss of smart functionality after switching supplier.
Heat network disputes (from April 2025): Billing, customer service, installation failures, and loss of heat or hot water from heat network suppliers holding an Ofgem authorisation.
Before You Write to the Energy Ombudsman: The Letter to Your Supplier
You must have formally complained to your supplier before the Energy Ombudsman can accept your case. If you have not yet done this, or if you are not certain your contact with the supplier was logged as a formal complaint, do this first.
Write to your supplier’s complaints team specifically, use the word ‘complaint’ clearly, state what went wrong, when it happened, and what you want the supplier to do. Send by email so you have a dated record. Note the date you sent it, as this starts the eight-week clock.
If your supplier does not respond within eight weeks, or responds but does not resolve the complaint to your satisfaction, you are ready to go to the Energy Ombudsman.
How to Submit Your Complaint: Online, Phone or Post
The Energy Ombudsman accepts complaints online at energyombudsman.org, by phone on 0330 440 1624, by email at enquiry@energyombudsman.org, or by post to Energy Ombudsman, PO Box 966, Warrington, WA4 9DF. The online portal is the fastest route and generates an immediate reference number. If you cannot use the online service, call the number and they can help you submit by phone or connect you to translation or BSL support if needed.
How to Write Your Complaint Letter or Submission
Whether you submit online, by email or by post, your complaint needs to cover the same core information. The following structure works for all energy complaint types.
Your Details and Account Information
Include your full name, address, date of birth, your energy account number, and the meter point reference number (MPAN for electricity or MPRN for gas) if you have it. These are on your bills and help the Ombudsman identify your account quickly. Include your supplier’s name and your complaint reference number if the supplier gave you one.
What Went Wrong and When
Describe the problem chronologically. Start with when you first noticed the issue or received the disputed bill. What did the supplier tell you? What did you do in response? Keep this factual and specific: dates, amounts, names of agents you spoke to if you have them. Avoid vague descriptions. A billing error of £340 first noticed in January, raised by phone in February with reference number X, disputed in writing in March, still unresolved is far more useful than ‘my bill has been wrong for months.’
What the Supplier Did or Did Not Do
Describe how the supplier responded to your complaint, or note that they did not respond. If they gave you reasons for their position, summarise those reasons and explain why you disagree with them. If you received a deadlock letter, say so and give the date.
The Impact on You
Describe specifically how the problem has affected you. Financial loss is the most important: how much have you been overcharged, how much credit has not been refunded, what costs have you incurred as a direct result of the supplier’s error. Also describe any non-financial impact: time spent trying to resolve the complaint, distress, inconvenience, difficulty managing your finances because of an incorrect direct debit.
What You Want the Ombudsman to Order
Be specific. Ask for the financial remedy you believe is fair: a refund of the overcharged amount, a corrected bill, a credit balance refund, compensation for the time spent and distress caused. The Energy Ombudsman can award up to £10,000 in financial compensation for domestic consumers. It can also order the supplier to apologise, correct your account, update your records and take specific remedial steps.
Full Worked Example: Billing Error Complaint
[Your full name]
[Your address]
[Your energy account number]
[Your MPAN or MPRN if known]
[Date]
Energy Ombudsman
PO Box 966, Warrington, WA4 9DF
[or submitted online at energyombudsman.org]
Subject: Complaint Against [Supplier name] – Billing Error – Account [number]
I am writing to submit a formal complaint to the Energy Ombudsman about my energy supplier, [supplier name]. I have completed [supplier name]’s complaints process and have not received a satisfactory resolution. [Eight weeks have now passed since I first formally complained / I received a deadlock letter on [date]].
What went wrong
In [month and year], I received a bill from [supplier] for £[amount] covering the period [dates]. This bill was significantly higher than my previous bills and appeared to be based on estimated rather than actual meter readings. My actual meter reading on [date] was [reading], which I submitted to the supplier on [date]. The reading submitted by the supplier for the billing period was [reading], which is incorrect.
[Continue with chronology: I contacted [supplier]’s customer service on [date] by [phone/email] and raised this as a formal complaint, reference number [number]. I was told [describe what you were told]. On [date] I received a response from [supplier] stating [summarise their position]. I disagree with this response because [explain why: the meter reading they used was an estimate that significantly overstates my actual usage / the Ofgem back-billing rules mean I should not be charged for energy used before [date] due to the supplier’s own error in failing to bill me during that period].]
Impact on me
As a result of this error, I have been overcharged by approximately £[amount]. [Supplier] has also increased my direct debit to £[amount] per month to cover the disputed balance, which I cannot afford. I have spent approximately [X hours] trying to resolve this complaint by phone and email over [X months]. The uncertainty about my account balance has caused me significant financial stress and inconvenience.
What I am asking for
I am asking the Energy Ombudsman to direct [supplier name] to: correct my bill to reflect my actual meter readings; refund the amount I have been overcharged; restore my direct debit to a level that reflects my actual usage; and pay compensation for the time and distress caused by this error.
Evidence attached
[List all documents: copies of the disputed bills / my formal complaint email dated [date] / [supplier]’s response dated [date] / the deadlock letter dated [date] if applicable / meter reading photographs with dates / records of calls and their reference numbers]
Yours sincerely,
[Your name]
[Contact details]
What Happens After You Submit
The Energy Ombudsman will acknowledge your complaint and contact your supplier to request their file on the matter. A case handler will review both sides and may contact you for further information. Many cases are resolved at this early stage through what the Ombudsman calls Facilitated Complaint Resolution, where the supplier makes an offer to settle. You are not obliged to accept this offer.
If the case is not resolved early, it proceeds to a full investigation. The Ombudsman issues a proposed resolution, which sets out what it considers fair. You can accept or reject this. If you accept, the supplier must implement it within around 28 days. If you reject it, you can take the matter to court instead, but you cannot return to the Ombudsman on the same complaint.
If the Ombudsman upholds your complaint and issues a final decision, the supplier must comply. If they do not, the Ombudsman can escalate to Ofgem. The whole process typically takes six to twelve weeks from submission to proposed resolution.
Getting Help
Free advice on energy complaints is available from Citizens Advice (0808 223 1133) and from the Energy Ombudsman’s own advice pages at energyombudsman.org. If you want help drafting a formal complaint letter to your supplier before the eight-week clock runs, or a submission to the Energy Ombudsman that is clearly structured and covers everything they need to assess your case, the team at LetterLab can help you get it right before you send it.
Quick Checklist: Before You Submit to the Energy Ombudsman
Have you formally complained to your supplier using the word ‘complaint’ and have a dated record of doing so?
Has either eight weeks passed without resolution, or have you received a deadlock letter?
Are you within 12 months of the supplier’s final response or deadlock letter?
Have you gathered your account number, meter reference number, all bills, and copies of all correspondence?
Have you calculated the specific financial amount you have lost or been overcharged?
Have you described the impact on you clearly, including both financial loss and time or distress?
Have you stated specifically what you want the Ombudsman to order?
Are you submitting online, by phone on 0330 440 1624, or by post to PO Box 966, Warrington, WA4 9DF?
The Key Takeaway: Eight Weeks, Deadlock Letter, Then Escalate
The Energy Ombudsman exists precisely because energy suppliers do not always resolve complaints fairly or at all. Its decisions are binding, its service is free, and it can order compensation of up to £10,000. Most people who have a legitimate energy complaint and do not use the Ombudsman simply do not know this route exists, or assume the process is too complicated. It is not.
Complain to your supplier first, in writing, and note the date. Wait eight weeks or request a deadlock letter. Then submit to the Ombudsman with your evidence. The process is straightforward and the outcome, when complaints are upheld, is enforceable.
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