The short answer
Choose a fixed energy tariff if the full annual cost is competitive and you value price certainty. Stay variable if you want flexibility, no fixed-term exit risk, and you are comfortable with prices moving when the Ofgem price cap changes. The right answer depends on your usage, unit rates, standing charges and exit fees — not just the monthly direct debit.
A fixed energy tariff and a variable tariff are not two versions of the same thing. A fixed tariff locks agreed rates for a set period. A standard variable tariff can change, and default tariffs are usually shaped by the energy price cap.
To compare them properly, ignore the headline monthly payment at first. Compare the unit rates, standing charges, contract length, exit fees and your realistic annual usage.
Fixed tariff vs variable tariff: what each means
Fixed energy tariff
A fixed tariff gives you agreed gas and electricity rates for a set contract term. Your bill can still rise if you use more energy, but the agreed rates stay fixed during the contract.
- Good for price certainty and budgeting.
- Can protect you if variable prices rise.
- May include exit fees if you leave early.
- Can cost more if market prices fall later.
Variable energy tariff
A variable tariff can change. If it is a default standard variable tariff, the price is usually affected by Ofgem’s price cap and can move when the cap changes.
- Usually more flexible than a fixed-term deal.
- Can benefit if capped prices fall.
- Can rise when the price cap rises.
- May be more expensive than competitive fixed deals.
How the Ofgem price cap affects variable tariffs
Ofgem says the price cap limits the maximum suppliers can charge people on default tariffs for each unit of energy and the daily standing charge. It is not a cap on your total bill.
For 1 July to 30 September 2026, Ofgem says the typical Direct Debit dual-fuel price-cap figure is £1,862 per year. The average Direct Debit rates are electricity at 26.11p/kWh with a 57.19p/day standing charge, and gas at 7.33p/kWh with a 29.04p/day standing charge.
| Cap element | What it controls | What it does not control |
|---|---|---|
| Unit rate | The price for each kWh of gas or electricity on default tariffs. | Your total usage. |
| Standing charge | The fixed daily charge for being connected. | Whether you use much energy that day. |
| Typical annual figure | An illustrative household using typical amounts. | A guaranteed maximum bill. |
A fixed tariff does not mean a fixed bill
This is the most common misunderstanding. A fixed tariff usually fixes the unit rates and standing charges, not your total monthly or annual bill. If you use more energy, you still pay more.
annual cost = electricity kWh × electricity unit rate
+ gas kWh × gas unit rate
+ daily standing charges × days
+ VAT and any tariff-specific charges
That is why two households on the same fixed tariff can have very different bills. Usage still matters.
Exit fees and the 49-day rule
Fixed tariffs can include exit fees. Citizens Advice says if you are on a fixed tariff, you can switch if you have 49 days or less left on your contract. If you have 50 days or more left, you might have to pay an exit fee.
Ofgem also warns that you may have to pay an exit fee if you switch tariffs or suppliers before your fixed rate tariff ends. That does not mean switching is always wrong. It means the exit fee should be included in the calculation.
Do not compare only the monthly payment
If a new tariff saves £120 a year but costs £150 in exit fees, the headline saving may disappear. Always compare the net benefit.
net switching benefit = estimated annual saving - exit fees - any other switching costs
Decision checklist: should you fix or stay variable?
Use this before signing a fixed deal or staying on a standard variable tariff.
Compare annual cost, not direct debit
Use your real annual kWh usage and the tariff rates. A low monthly payment can be misleading if it is based on low estimated usage.
Check unit rates and standing charges
A tariff can have lower unit rates but higher daily charges, or the other way around. Usage level changes which is better.
Check exit fees and contract length
A 12-month fix, 18-month fix and 24-month fix have different risks. Longer certainty can also mean longer commitment.
Ask what happens if prices fall
If variable rates fall after you fix, you may not benefit unless you switch and absorb any exit fees.
Check whether the deal has conditions
Some deals may require a smart meter, Direct Debit, online billing or dual-fuel supply.
When a fixed tariff may make sense
A fixed tariff may be worth considering when the annual cost is competitive, exit fees are acceptable, and you value certainty more than the chance of benefiting from falling variable rates.
You want certainty
Fixed rates can help households plan, especially when price-cap changes are uncertain.
You expect increases
If variable rates rise, a good fixed deal can protect against future increases during the term.
The numbers beat variable
If the fixed annual cost is lower after fees, it may make financial sense.
When staying variable may make sense
A standard variable tariff may suit households that value flexibility, are close to moving, do not want exit-fee risk, or believe fixed deals are currently priced too high.
You may switch soon
Variable tariffs are usually easier to leave than fixed-term deals.
You expect rates to drop
Staying variable may let you benefit if default tariff rates fall in a future cap period.
You dislike penalties
A variable tariff avoids being locked into a deal that may later look less attractive.
Example: how to compare a fixed deal with variable
Use your own usage, but the comparison process is always the same.
| Comparison step | Variable tariff | Fixed tariff | Decision point |
|---|---|---|---|
| Electricity rate | Use current variable rate. | Use quoted fixed rate. | Which is lower for your usage? |
| Gas rate | Use current variable rate. | Use quoted fixed rate. | Which is lower for your usage? |
| Standing charges | Use daily charges × 365. | Use quoted fixed standing charges × 365. | Higher standing charges matter more for low-use homes. |
| Exit fees | Usually none on standard variable tariffs. | May apply if you leave early. | Subtract fees from any expected saving. |
Run the comparison with your figures
Enter each tariff into the bill estimator using your annual gas and electricity usage.
Fixed tariff vs fixed Direct Debit
Do not confuse a fixed energy tariff with a fixed monthly Direct Debit. A fixed tariff is about the rates you pay. A fixed monthly Direct Debit is a payment method that spreads expected cost across the year.
You can have a fixed monthly Direct Debit on a variable tariff. You can also have a fixed tariff where your monthly payment changes if your usage is much higher or lower than expected.
Check both parts separately
Tariff decides the rates. Usage decides how much energy you buy. Direct Debit decides how you pay.
What about smart, tracker or time-of-use tariffs?
Some tariffs do not fit neatly into “fixed vs variable”. A tracker tariff may follow wholesale prices. A time-of-use tariff may charge different prices at different times. Economy 7 gives cheaper overnight electricity and higher daytime rates.
These can be useful if your home has flexible demand, an electric vehicle, battery storage, electric heating, solar panels or appliances you can run at cheaper times. They can be poor value if your usage does not match the tariff structure.
Common mistakes when comparing tariffs
- Comparing monthly direct debit instead of annual cost.
- Forgetting exit fees on a fixed tariff.
- Assuming a fixed tariff means a fixed total bill.
- Ignoring standing charges and only comparing unit rates.
- Using national average usage instead of your real annual kWh.
- Forgetting that price-cap figures are for typical usage, not a maximum bill.
- Not checking whether a deal requires a smart meter, Direct Debit or online account.
FAQs
Is a fixed energy tariff better than a variable tariff?
It depends on price, usage, exit fees and whether you value certainty. A fixed tariff can protect you from rises, but it can also stop you benefiting if variable prices fall.
Does a fixed tariff fix my whole energy bill?
No. It usually fixes the rates, not the total bill. Your total still depends on how much gas and electricity you use.
Can I switch away from a fixed tariff?
Yes, but you may have to pay exit fees unless you are near the end of the contract. Citizens Advice highlights the 49-day rule for switching near the end of a fixed contract.
Does the price cap apply to fixed tariffs?
The price cap applies to default tariffs. Fixed tariffs have agreed rates for the contract term, so compare the fixed rates against the current and expected variable rates.
What should I check before fixing?
Check unit rates, standing charges, annual usage, contract length, exit fees, payment method, smart meter requirements and whether the quoted annual cost uses realistic consumption.