A fixed tariff vs variable decision can affect more than the number on your monthly direct debit. It determines how exposed you are to energy price changes, whether you may face exit fees, and how predictable your household costs feel over the next year or two.
For most households, the right choice is not simply whichever tariff has the lowest headline price. You need to look at your energy use, the contract length, the standing charge and how comfortable you are with the risk of prices moving after you sign up.
A fixed energy tariff locks the unit rate you pay for gas and electricity for a set period, often 12 months, though deals can be shorter or longer. The unit rate is the price per kilowatt hour (kWh) of energy you use. In many cases, the daily standing charge is fixed too, but always check the tariff details rather than assuming.
The key word is rates, not bills. A fixed tariff does not mean you will pay the same amount every month or year. If you use more heating during a cold winter, charge an electric vehicle, or spend more time working from home, your bill will rise because you have used more energy.
The main benefit is certainty. If wholesale energy prices rise and suppliers increase prices on variable tariffs, your fixed unit rates stay the same until your deal ends. This can make household budgeting easier, particularly when money is tight.
There can be a cost for that certainty. Fixed deals may include exit fees if you leave before the end date. These fees vary by supplier and fuel, so check the terms before switching. A tariff that looks cheap can be less flexible if you expect to move home or want the freedom to switch quickly.
A variable tariff, sometimes called a standard variable tariff, has rates that can go up or down. The supplier can change its prices, usually with notice, and your costs will follow those revised rates and your usage.
Most UK households on a variable tariff are protected by Ofgem's energy price cap. This limits the amount suppliers can charge per unit of energy and for standing charges for typical domestic customers. It is useful protection, but it is not a cap on your total bill.
Your actual bill still depends on how much gas and electricity you use. A larger home, a poorly insulated property or a household with several people will generally pay more than the illustrative annual figure quoted alongside the price cap.
Variable tariffs are often more flexible than fixed deals. They normally have no exit fee, which means you can switch when a better offer appears. That flexibility can be valuable when prices are falling, but it also leaves you exposed if rates rise.
The practical difference comes down to price certainty versus flexibility. A fixed tariff gives you known unit rates for the agreed term. A variable tariff gives you the freedom to leave more easily, but the rates can change during the year.
Neither option automatically saves money. A fixed deal might be cheaper than the current price-capped variable rate when you take it out. Equally, it may become more expensive later if the price cap falls. A variable tariff may look sensible when forecasts suggest lower prices ahead, but forecasts are not guarantees and energy markets can change quickly.
Standing charges deserve attention too. This daily amount is paid whether or not you use energy. It varies by region, fuel and tariff. For a low-usage household, such as a person living alone in a well-insulated flat, a higher standing charge can make a noticeable difference to the annual cost. For a household using lots of energy, the unit rate often has greater impact.
Payment method can also affect pricing. Monthly direct debit tariffs are commonly priced differently from prepayment or payment on receipt of bill options. Do not compare a tariff based only on a supplier's advertised monthly figure. Compare the unit rates, standing charges and estimated annual cost for your own usage.
A fixed tariff can be a practical choice if your priority is a predictable budget. It may suit households that would struggle with a sharp increase in energy costs, or those who simply prefer knowing that their rates will not change over winter.
It can also make sense when the fixed deal is meaningfully cheaper than the variable tariff available to you, even after allowing for the possibility that prices could fall. Check how long the fix lasts. A 12-month deal gives a different level of commitment from a two-year deal, especially if there are exit fees.
Before choosing, think about your circumstances. If you are likely to move home soon, a long fix may be inconvenient. Suppliers usually allow you to close or transfer an account when you move, but the rules differ, so read the terms rather than relying on assumptions.
A variable tariff may suit you if flexibility matters most. With no exit fee, you can take advantage of a new fixed deal if one becomes attractive later. This is useful for people who are willing to keep an eye on their energy costs and review their tariff regularly.
It can also be reasonable if fixed deals are currently priced above the variable rate and you do not want to pay extra for certainty. The trade-off is straightforward: your rates may rise at the next price cap change or when your supplier revises its tariff.
Some households should also look beyond the usual fixed versus variable choice. If you have a smart meter and can shift electricity use to quieter periods, a time-of-use tariff could be worth considering. These tariffs can offer cheaper electricity at certain times, but they are only good value if you can genuinely move usage, such as charging an electric vehicle overnight or running appliances off-peak.
Start with your annual energy use in kWh, not just your direct debit amount. You can find this on a recent bill or annual statement. Direct debits are estimates and may include a credit or debit balance, so they are not a reliable measure of the underlying tariff price.
Then compare tariffs using the same details: your postcode, payment method, gas and electricity usage, unit rates, standing charges, contract end date and exit fees. Prices vary across the UK, so a deal that works for a neighbour in another area may not be available or priced the same for you.
If you are comparing dual fuel with separate gas and electricity suppliers, add up the total annual cost rather than assuming dual fuel is cheaper. It can be convenient to have one supplier, but convenience does not always mean better value.
Also check what happens when a fixed term ends. Suppliers should contact you before your deal finishes, but it is still worth setting a reminder. If you do nothing, you will usually move onto a variable tariff. That may be fine, but it should be a deliberate choice rather than an expensive oversight.
Choose a fixed tariff if you value certainty, the price is competitive for your usage and you are comfortable committing for the term. Choose a variable tariff if you need the freedom to switch, do not want exit fees and can accept that your rates may change.
Avoid making the decision based on predictions alone. No one can say with certainty where energy prices will be in six or twelve months. A better approach is to decide what level of cost risk your budget can handle, then choose the tariff that fits it.
Before you switch, take ten minutes to read the tariff information label and contract terms. A clear choice based on your own usage is usually worth more than chasing a headline saving that does not match the way your household actually uses energy.