Comparison · Electricity and gas plans

Fixed-rate or variable energy plan: how to decide

Last updated 25 October 2026 · 2 sources listed · Reading time about 4 minutes

Short answer

A fixed plan holds the unit rate for the contract term, which gives budgeting certainty but usually comes with an exit charge and no benefit if wholesale costs fall. A variable plan moves with the supplier's costs or a published index, so bills can rise or fall without notice. Compare how rates are set, what ends the lock, and what leaving early costs.

Who this is for: A household with an electricity or gas supply contract coming to an end, weighing price certainty against flexibility.

What to evaluate

Exposure to wholesale movement
Fixed plans transfer wholesale risk to the supplier for a period; variable plans pass it on, usually with a delay.
How to check: Ask what triggers a variable rate change and how much notice you receive before it applies.
Standing charge treatment
The daily fixed element is often unchanged by headline rate promotions, yet it shapes low-use households' bills heavily.
How to check: Read the daily charge line on the contract summary and compare it between offers as well as the unit rate.
Exit and early-termination terms
A fixed plan that penalises leaving can turn a good decision into a trap if you move home.
How to check: Find the exit fee clause, whether it applies on house moves, and whether it is waived near the end date.
What happens at term end
Many fixed plans roll onto a default rate that is less favourable than the one you signed.
How to check: Look for the roll-over rate wording and the window in which the supplier must notify you.
Regulatory protection
In some countries the regulator sets rules on notice periods, price caps or switching rights that change how risky each type is.
How to check: Check your energy regulator's website for rules on notice, cooling-off and any cap that applies to your plan type.
Your own usage pattern
Heavy winter heating use makes you more sensitive to rate changes than a low, flat consumer.
How to check: Review a year of bills and see how much of your cost sits in the coldest months.

Comparison

How the two plan structures compare in practice
Plan type	Good when	Watch out for
Fixed for the full term	You value predictable budgets and expect market costs to rise or stay volatile	Exit charges, no gain if costs fall, a poor roll-over rate
Variable on supplier discretion	You want freedom to leave without penalty and tolerate bill swings	Rate rises that follow market moves quickly but falls that lag
Tracker tied to a published index	You want transparent logic and are comfortable with movement both ways	A margin that sits on top of the index and a base rate you cannot see changing
Short fixed term with easy renewal	You want certainty but dislike being locked in for long	Frequent renewal admin and the risk of lapsing onto the default rate

Decision worksheet

Rate up to three options against this guide’s own criteria. It runs in your browser and saves only on this device. It is a thinking aid, not a recommendation.

1. Have you checked each criterion?

Exposure to wholesale movement — Ask what triggers a variable rate change and how much notice you receive before it applies.
Standing charge treatment — Read the daily charge line on the contract summary and compare it between offers as well as the unit rate.
Exit and early-termination terms — Find the exit fee clause, whether it applies on house moves, and whether it is waived near the end date.
What happens at term end — Look for the roll-over rate wording and the window in which the supplier must notify you.
Regulatory protection — Check your energy regulator's website for rules on notice, cooling-off and any cap that applies to your plan type.
Your own usage pattern — Review a year of bills and see how much of your cost sits in the coldest months.

0 of 6 criteria checked.

2. Compare options (0 = fails or unknown, 3 = meets it well)

Criterion	Option 1 name	Option 2 name	Option 3 name
Exposure to wholesale movement	Exposure to wholesale movement score for Option A	Exposure to wholesale movement score for Option B	Exposure to wholesale movement score for Option C
Standing charge treatment	Standing charge treatment score for Option A	Standing charge treatment score for Option B	Standing charge treatment score for Option C
Exit and early-termination terms	Exit and early-termination terms score for Option A	Exit and early-termination terms score for Option B	Exit and early-termination terms score for Option C
What happens at term end	What happens at term end score for Option A	What happens at term end score for Option B	What happens at term end score for Option C
Regulatory protection	Regulatory protection score for Option A	Regulatory protection score for Option B	Regulatory protection score for Option C
Your own usage pattern	Your own usage pattern score for Option A	Your own usage pattern score for Option B	Your own usage pattern score for Option C
Total (max 18)	0	0	0

Questions to ask before you commit

Is the unit rate fixed for the whole term, or only the energy portion with network and policy costs passed through?
What is the standing charge and is it fixed too?
What exit charge applies, and does it apply if I move home?
What rate will I move to when the term ends, and when will you tell me?
Can I leave without penalty during a window before the end date?
Is there any credit or discount that disappears after an introductory period?
Are there extra requirements such as direct debit, paperless billing or a smart meter to keep the quoted rate?
Where do I complain, and is there an independent ombudsman or similar body?

Typical trade-offs

Lock in for a longer term

Upside: Predictable monthly outlay and protection against sudden market spikes
Downside: You may miss out if costs fall and may face a fee if circumstances change

Stay variable to keep flexibility

Upside: You can switch whenever a better offer appears without penalty
Downside: Bills can rise with little warning and are harder to budget

Pick a tracker for transparency

Upside: You can see why the rate moves and trust it follows a public reference
Downside: Month-to-month volatility with no ceiling in some designs

Common mistakes

Comparing only the headline unit rate and ignoring the standing charge, which can reverse the ranking for low-use homes.
Letting a fixed plan lapse onto the default rate because no reminder was diarised; set a calendar prompt before the notice window opens.
Assuming a fixed plan means a fixed bill; you still pay for the units you use, so consumption swings still move the total.
Signing a long fixed term shortly before a planned house move without checking whether the exit fee applies to moves.
Treating a supplier's own comparison page as neutral when it may list only its own plans; use an accredited or regulator-run comparison tool where one exists.

Sources and further reading

These pages were reachable when we last checked. They informed definitions and rules referred to above; they do not endorse this guide. Where rules differ by country, check the authority for your location.

Ofgem consumer guidance — Ofgem, retrieved 27 October 2026
ACER energy regulation overview — EU Agency for the Cooperation of Energy Regulators, retrieved 27 October 2026

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