Fixed or variable gas: which formula to choose

Updated on September 1, 202613 plans compared13 providers

In short

A fixed gas contract locks your energy price for the whole term. A variable one follows a published index and moves with the market. The choice is not about finding the cheaper option in advance — nobody can — but about deciding whether you are buying a price or buying predictability.

Belgian gas contracts by pricing formula, with the energy price and the annual standing charge.
Provider	Plan	Price	Key points	View plan
MegaPartner	Prepaid Flex	6.53 c€/kWh	Variable rate Annual standing charge €177,83 Prepaid plan	View plan
Octa+Partner	Flux	6.14 c€/kWh	Variable rate Annual standing charge €200,43 Independent Belgian supplier	View plan
DATS 24	Gaz Naturel Variable	4.64 c€/kWh	Variable rate Annual standing charge €173,93 Subsidiary of the Colruyt group	View plan
EnergyVision	Gaz bon marché 1 an fixe	5.80 c€/kWh	Fixed rate Annual standing charge €210,43 Price guaranteed for one year	View plan
Ecofix	Flexy Online	6.17 c€/kWh	Variable rate Annual standing charge €145,43 Among the lowest standing charges	View plan
Engie	Basic Variable	6.34 c€/kWh	Variable rate Annual standing charge €155,43 Belgium's largest supplier	View plan
Luminus	BasicFlex Gaz	6.48 c€/kWh	Variable rate Annual standing charge €155,43 Belgium's second-largest supplier	View plan
TotalEnergies	myEssential Variable	6.58 c€/kWh	Variable rate Annual standing charge €170,43 Discount on TotalEnergies fuel	View plan
Eneco	Gaz Naturel Flex	7.02 c€/kWh	Variable rate Annual standing charge €200,43 Belgian supplier	View plan
Bolt	Plenty Variable Online	7.24 c€/kWh	Variable rate Annual standing charge €147,31 No termination fee	View plan
Elegant	Elegant Gaz	On request	Independent Belgian supplier Monthly tariff sheet on request Fixed and variable plans	View plan
Frank Energie	Frank Gas	On request	Market purchase price with no margin on energy Fixed monthly subscription Consumption management app	View plan
Trevion	Trevion Gaz	On request	Independent Belgian supplier Offers for households and small businesses Tariff sheet on request	View plan

Prices and features surveyed on August 31, 2026. They may have changed since. Always check the offer on the provider’s website before signing up.

What each formula actually does

A fixed price is set on the day you sign and does not move for the term, typically one to three years. Your winter bill is knowable in advance, which is the entire point.

A variable price follows a published index, revised monthly or quarterly. It falls when wholesale gas falls and rises when it rises, and your supplier publishes the index it uses in the tariff card.

A dynamic price follows the hourly market. It suits consumption you can move — a dishwasher, a car charger — and gas is the one energy you essentially cannot move, since you heat when the house is cold.

What you are paying for with a fixed price

The supplier who sells you a fixed price has to buy that gas forward, and hedging costs money. That cost is embedded in the price you are quoted, which is why fixed contracts sit above variable ones at the moment of signing almost every time.

The question is therefore not whether the fixed price is higher today — it is — but whether the market will rise enough during the term to make up the gap. That is a bet on gas prices, and it is not a bet a household is better placed to win than a trading desk.

The cost of leaving before the end

Belgian residential energy contracts can be terminated with one month's notice, and no exit fee may be charged to a household — that protection is written into federal consumer law and applies to fixed contracts too.

What you lose by leaving a fixed contract early is the price itself, not a penalty. If the market has fallen far enough, leaving is simply the right move, and nothing in the contract prevents it.

Our verdict

Over long periods, variable contracts have generally cost less than fixed ones in Belgium, because the premium charged for certainty is real and permanent. Fixed pricing buys you a budget, not a saving. If an unpredictable winter bill would genuinely put your household under strain, that premium is worth paying; otherwise it rarely is.

Frequently asked questions

Is a fixed gas price safer?

It makes your bill predictable, which is a different thing from cheaper. You pay a premium for that predictability at signing, and if the market falls during the term you keep paying the old price. Fixed pricing protects a budget; it does not protect a wallet.

How often does a variable gas price change?

Monthly or quarterly, depending on the contract. The tariff card names the index used and the revision frequency, and both are worth reading: two contracts described as variable can follow different indices and move at different speeds.

Can I leave a fixed gas contract early?

Yes. A Belgian household may end an energy contract with one month's notice, and no exit fee can be charged, whatever the contract's stated term. What you lose is the fixed price you had secured, not money paid as a penalty.

Does a dynamic tariff make sense for gas?

Rarely. A dynamic price rewards consumption you can shift to cheaper hours, and heating is not shiftable — you heat when the house is cold. Dynamic pricing pays off on electricity, where a car charger or a heat pump can be scheduled, far more than on gas.