How to write a formal complaint to your energy supplier UK
Energy suppliers are very good at one thing: outlasting you.
Endless hold music. Generic acknowledgement emails. Frontline agents who have no authority to resolve anything. A complaints process designed to exhaust customers until they give up and move on.
Most people do give up. That's why it works. This guide is for the ones who don't — covering your legal rights, what a formal energy supplier complaint letter UK must contain, the compensation you may already be owed, and the escalation path that energy companies genuinely do not want you to take.
What you're entitled to — even before you complain
Before you write a single word, understand what the law requires of your supplier. A strong complaint doesn't appeal to goodwill — it cites obligations.
The Gas Act 1986 and the Electricity Act 1989 establish the licensing framework under which every UK domestic energy supplier operates. Those licences are granted and enforced by Ofgem, and they come with binding obligations about how suppliers must treat customers — including complaint handling standards. When your supplier ignores you, they may be in breach of their licence conditions.
The Consumer Rights Act 2015, section 49 requires that services provided to consumers be carried out with reasonable care and skill. Wrongly estimated bills, charges you didn't agree to, a botched account switch — these are service quality failures with a statutory basis, not just things to be unhappy about.
Then there are Ofgem's Guaranteed Standards of Performance — specific response obligations with defined compensation amounts if suppliers fail to meet them. These aren't goodwill gestures. They are automatic payments your supplier is required to make:
£30 — missed engineer appointments
If your supplier's engineer fails to arrive within the agreed appointment window, you are automatically entitled to £30 under Ofgem's Guaranteed Standards of Performance.
£30 — billing dispute not investigated in time
If your supplier fails to investigate and respond to a billing dispute within the required timeframe after directing you to contact them, that's a further £30 payment owed.
£30 — failure to restore supply within 24 hours
If your gas supply is interrupted by a fault caused by your supplier's equipment and they fail to restore it within 24 hours, compensation is owed under the Guaranteed Standards.
If these payments haven't been made, that goes in your letter — by name, with the amount.
How to complain to your energy supplier: step by step
Follow this sequence. Every step matters — and every step creates a record.
Exhaust the internal process first
Contact your supplier formally — by email or in writing, not just by phone — setting out what happened and when, what you have already been told, what you want them to do, and a reasonable deadline of 10–14 working days. Keep a record of everything: dates, agent names, reference numbers, and what was said.
Escalate internally if the first response fails
If the initial response doesn't resolve things, ask for the complaint to be escalated to their customer resolution team or complaints department. Reference their own complaints procedure in your letter — this matters when you escalate to the regulator.
Trigger the 8-week clock
Once you raise a formal complaint, your supplier has 8 weeks to resolve it to your satisfaction — Ofgem requires this. If unresolved after 8 weeks, or if you receive a deadlock letter, you can take the matter to the Energy Ombudsman UK. Make sure you log the start date clearly in writing.
Issue a formal complaint letter
A phone call is not a formal complaint. Send your letter by email to the official complaints address (which your supplier must publish) and follow up by recorded post if needed. State clearly it is a formal complaint, cite specific dates and account references, name the relevant legislation, and state the escalation route if unresolved.
⚠ The 8-week deadline and the deadlock letter
Once you raise a formal complaint, the clock starts. Your supplier has 8 weeks to resolve it. If they haven't done so after 8 weeks — or if they issue a deadlock letter (written confirmation they cannot resolve the complaint) — you can immediately refer the matter to the Energy Ombudsman UK.
If you've been bounced around for weeks without a formal complaint being logged, write today clearly stating: “I am raising a formal complaint as of [today's date].” The 8-week period starts from that date.
Don't let this drift. Suppliers rely on delay. Pin the start date down in writing.
What makes a strong energy supplier complaint letter
Most complaint letters fail because they are vague, emotional, or rely on the supplier feeling shame. None of those things work. A letter that gets results does five specific things:
Cites their own terms and conditions
Every energy supplier has a complaints procedure published in their T&Cs. Referencing it — and showing they have not followed it — is more powerful than simply stating you are unhappy.
References the Ofgem code
Ofgem's Standards of Conduct require suppliers to treat customers fairly, provide accurate information, and handle complaints promptly. If your supplier has failed on any of these, name the standard explicitly.
Quantifies the harm specifically
Don't say "I've been overcharged." Say "I have been charged £347.50 above the agreed direct debit amount for the period January–March 2026, without prior notice, in breach of your own billing terms."
Sets a specific deadline
"Please respond by [date]" creates a record and triggers the 8-week clock clearly. It is far more effective than "please respond as soon as possible."
Names the escalation route
"If this matter is not resolved within 8 weeks, I will refer it to the Energy Ombudsman UK." Frontline agents know what this means. Complaints teams certainly do.
Fight My Corner
Ready to fight back?
We write a legally grounded letter citing real UK legislation and their own policy deadlines. From £9.99.
Write my letter now →The legislation behind your complaint
Your complaint gains legal weight when it cites the framework your supplier operates within. You don't need to quote these in full — naming them signals that you know the regulatory landscape, and that a generic response won't close this down.
- Gas Act 1986 — licensing obligations on gas suppliers, enforced by Ofgem. A supplier in breach of their licence conditions is acting unlawfully.
- Electricity Act 1989 — equivalent framework for electricity suppliers, with the same Ofgem enforcement mechanism.
- Consumer Rights Act 2015, section 49 — services must be performed with reasonable care and skill. Billing errors, account mismanagement, and failed switches fall here.
- Ofgem Standards of Conduct — requirement to treat customers fairly, provide accurate information, and handle complaints promptly and professionally.
- Ofgem Guaranteed Standards of Performance — specific obligations with fixed compensation amounts (£30+) for defined failures including missed appointments, billing dispute delays, and supply interruptions.
If your supplier won't resolve it: the Energy Ombudsman UK
The Energy Ombudsman UK is an independent Alternative Dispute Resolution (ADR) scheme, approved by Ofgem under the requirements of the Gas Act 1986 and Electricity Act 1989. It is free to use and has real powers. It can require your supplier to:
- Issue a formal apology
- Provide a full explanation of what went wrong
- Take specific corrective action (e.g. correct a bill, reconnect a supply)
- Pay financial compensation
You can refer your case once either:
- 8 weeks have passed since you raised a formal complaint, or
- You have received a deadlock letter from your supplier
Citizens Advice (0808 223 1133) can provide free, independent guidance on your complaint before and during this process. Their energy helpline is a useful first port of call if you're unsure how to frame the complaint or what you can claim.
To refer to the Energy Ombudsman: www.ombudsman-services.org/sectors/energy
Write your energy supplier complaint letter now
Fight My Corner generates formally grounded complaint letters for energy supplier disputes — citing the Gas Act 1986, the Consumer Rights Act 2015, Ofgem's Guaranteed Standards, and your supplier's own obligations. Tailored to your situation and ready to send in under a minute.
Single Dispute Letter £9.99. Full Case Escalation £19.99.
Write your energy complaint letter now →Fight My Corner provides dispute letter generation tools and guidance — not legal advice. For complex energy billing disputes involving large sums or potential court action, consider seeking independent legal advice. Citizens Advice can provide free guidance on your options.