Before You Switch Energy Supplier: Risks, Traps and What to Check First

Energy Key Facts: Switching Energy Supplier Switching window: typically 17 days Debt block threshold: over £500 owed Exit fee range: £0 to £150 per fuel Cooling off period: 14 days Complaints body: Energy Ombudsman Regulator: Ofgem

What actually happens when you switch energy supplier

When a switch is initiated, the new supplier contacts the old one and takes over supply on an agreed date. Under Ofgem's switching rules, the process takes around 17 days from sign-up to completion for most domestic customers. During that window, both suppliers exchange meter readings to produce a final bill from the old supplier and an opening statement from the new one. The switch itself does not require an engineer visit for most standard meters. Smart meter customers may find their meter temporarily reverts to basic mode if the new supplier uses a different network protocol, though Ofgem has been working to resolve smart meter interoperability issues since 2018. Crucially, the supply itself does not physically change. Gas and electricity are delivered through the same pipes and wires regardless of which company sends the bill. What changes is the contract, the tariff rate and the customer service relationship.

The risks most people do not check before switching

Outstanding debt blocks the switch. Under Ofgem's Supplier of Last Resort protections, a supplier can block a switch if a customer owes more than £500 per fuel. This catches people who have built up arrears on prepayment meters or who have disputed bills that remain unresolved. The block is legal and widely used. Clearing the debt or formally disputing it through the Energy Ombudsman before switching is the correct sequence. Exit fees can eliminate the saving. Fixed-rate tariffs typically carry exit fees of between £25 and £75 per fuel, meaning up to £150 for a dual-fuel household. On a modest saving of £100 per year, this wipes out most of the first year's benefit. Suppliers are required to disclose exit fees before sign-up, but comparison engines rarely weight them into the headline saving figure. Direct debit resets can cause surprises. New suppliers calculate opening direct debits based on estimate consumption, not your actual usage history. If your current supplier has set a low direct debit based on years of accurate readings, the new one may set it substantially higher. This is not a price increase but a cash flow difference that catches customers off guard in month one. Smart meter mode changes. First-generation SMETS1 smart meters frequently lose their smart functionality on a switch, reverting to a basic meter that requires manual readings. SMETS2 meters installed from 2018 onward are designed to retain functionality across switches, but this is not universally reliable. Check your meter generation with your current supplier before switching. Supplier failure risk. Between 2021 and 2023, over 30 UK energy suppliers failed. Ofgem's Supplier of Last Resort process protects credit balances up to a point, but customers frequently experienced weeks of uncertainty, lost tariff terms and forced migration to variable-rate contracts. Checking a prospective supplier's financial standing, while difficult for consumers, is a relevant consideration.

What the small print usually says

Energy contracts contain several clauses that comparison engines summarise or omit entirely. Tariff guarantee periods specify how long the advertised rate is fixed. Some tariffs fix unit rates but not standing charges, meaning the daily standing charge can rise during the contract period. The contract should specify whether both elements are fixed. Annual price review clauses in some variable contracts allow suppliers to alter rates with as little as 30 days notice. Ofgem requires notification but does not cap the increase outside of the energy price cap framework, which sets the maximum rate for standard variable tariffs, not fixed ones. Auto-rollover terms specify what happens at the end of a fixed contract. Most suppliers roll customers onto their standard variable tariff automatically. Some do not notify customers until after the rollover has occurred. Ofgem rules require notification 42 to 49 days before a fixed deal ends, but this window is short enough that customers who do not act promptly face weeks on a higher rate. Green tariff definitions vary significantly. Some green tariffs match consumption with Renewable Energy Guarantee of Origin certificates, meaning the electricity supplied is not literally from renewable sources but that an equivalent amount has been generated renewably somewhere. Others supply directly from renewable generation. The distinction matters for customers making purchasing decisions based on environmental impact.

Who switching works for and who it does not

Switching saves money in most circumstances for customers on a supplier's standard variable tariff who have no outstanding debt and whose fixed contract has ended or is approaching its end without significant exit fees. Switching is less straightforward for customers in rented accommodation where the landlord holds the energy contract, customers on prepayment meters with arrears, households with SMETS1 smart meters who rely on smart functionality for time-of-use tariffs, and businesses on longer-term contracts with material exit penalties. Customers in debt to their current supplier should prioritise resolving that debt first, either through a repayment arrangement or by formally disputing the balance via the Energy Ombudsman if it is contested. Initiating a switch while a debt is under dispute can complicate the resolution process.

What to verify before you proceed

Before initiating a switch, confirm the following directly with your current supplier, not via a comparison engine: The exact end date of your current tariff or contract. Whether exit fees apply and the precise amount per fuel. Your current outstanding balance or credit balance. Whether your meter is SMETS1 or SMETS2. Whether any direct debit arrears or disputes are unresolved. When evaluating a new supplier, check their Ofgem rating and Citizens Advice supplier performance scores, which rank suppliers on complaints handling, billing accuracy and customer service. The cheapest tariff from a supplier with poor complaint performance frequently costs more in time and stress than a modestly more expensive tariff from a reliable supplier.

Where to complain if a switch goes wrong

If a switch results in billing errors, a lost credit balance, or a supplier refusing to complete a transfer without justification, the correct escalation path is: First, raise a formal complaint in writing with the current or new supplier. Suppliers are required to resolve complaints within eight weeks. If unresolved after eight weeks, or if a deadlock letter is issued, the complaint can be escalated to the Energy Ombudsman, which adjudicates free of charge for domestic customers and can award compensation and direct remedial action. Ofgem does not handle individual complaints but can be notified of systemic issues.

Disclaimer This article is for information only and does not constitute regulated financial or energy advice. Tariff availability, exit fees and supplier policies change frequently. Always verify current terms directly with your supplier and any prospective new supplier before switching. Kael Tripton Ltd is an independent editorial publisher and is not regulated by Ofgem or the FCA.

Frequently asked questions

Can my current supplier refuse to let me switch?

A supplier can delay a switch if debt over £500 per fuel is outstanding. They cannot refuse a switch where no debt exists. If a supplier blocks a switch without justification, this is a complaint matter for the Energy Ombudsman.

Do I need to contact my old supplier to cancel?

No. The new supplier manages the switching process and notifies the old supplier. Customers do not need to cancel the old contract directly, though taking a meter reading on the switch date is advisable for billing accuracy.

What happens to my credit balance when I switch?

Suppliers are required to refund credit balances within 10 working days of the final bill being issued. If a supplier fails to do so, this is a complaint matter and the Energy Ombudsman can direct repayment.

Can I switch if I am on a prepayment meter?

Yes, though some tariffs are not available on prepayment meters. Debt on a prepayment meter above £500 per fuel will block the switch until resolved.

What is the Ofgem price cap and does it affect switching?

The Ofgem price cap sets the maximum unit rate and standing charge for domestic customers on default and standard variable tariffs. It does not cap fixed tariffs, which can be above or below the cap level. The cap is reviewed quarterly.

How long does a switch take?

Most switches complete within 17 days of sign-up under current Ofgem rules. Some suppliers offer faster switching but the minimum cooling-off period of 14 days applies regardless.

What if my new supplier goes bust after I switch?

Ofgem's Supplier of Last Resort process assigns customers to a new supplier and protects credit balances. Tariff terms are not guaranteed to be replicated and customers are typically placed on a standard variable tariff pending a new choice.

Sources Ofgem: Energy Price Cap Ofgem: Switching Your Energy Supplier Energy Ombudsman: How to Complain Citizens Advice: Supplier Performance Scores