Energy tariffs explained: fixed, variable and tracker

The building blocks of every energy bill

Before comparing tariff types, it helps to know what you are paying for. Most UK domestic bills combine a daily standing charge and a unit rate charged in pence per kilowatt-hour (p/kWh). Standing charges cover fixed costs of keeping you connected; unit rates cover the energy you use.

That is why the lowest unit rate is not always the cheapest deal for your home. High standing charges can outweigh a headline unit price, especially for lower-usage households. When you compare on Brillia, we estimate annual cost from the details you enter so you can rank deals by what you are likely to pay overall — not just one line of marketing copy.

Brillia Energy is a free comparison site from Zynx Ltd (trading as Brillia). We are not a supplier. Licensed suppliers are regulated by Ofgem. Understanding tariff structures helps you ask better questions and avoid rolling onto an expensive default when a fixed deal ends.

Fixed tariffs: certainty for a set period

A fixed tariff locks your unit rates (and often the standing charge terms) for a defined period — commonly 12 months. Households choose fixed deals when they want predictable bills and protection if wholesale prices rise.

The trade-off is flexibility. If the market falls, you may sit on a rate that is no longer competitive until the term ends. Many fixed deals charge an exit fee if you leave early. Always check the fee amount and remaining months before switching mid-contract.

Fixed does not always mean every line on the bill is frozen forever — read whether standing charges are fixed, and whether there are conditions such as Direct Debit or paperless billing. Deal cards and full details on Brillia surface the key terms so you can compare like for like.

If you are actively mid-switch or preparing to leave a fixed deal, our step-by-step how to switch energy supplier guide covers timings, documents and cooling-off.

Standard variable tariffs (SVT)

An SVT can change when the supplier updates prices. Many customers land on an SVT automatically when a fixed deal expires. SVTs are flexible — often easier to leave without an exit fee — but they are frequently more expensive than a carefully chosen fixed deal at the same moment in time.

Treat an SVT as a holding pattern, not a long-term plan, unless you have a specific reason to stay flexible. Set a reminder near the end of any fixed term and recompare before the roll-over date. That single habit saves many households more than tweaking thermostat settings alone.

Payment method still matters on SVTs. Monthly Direct Debit usually unlocks the most competitive pricing. Prepayment and pay-on-receipt options exist but can cost more. Match the deal to how you actually pay.

Tracker and index-linked tariffs

Tracker tariffs follow a published index, wholesale benchmark or formula. Prices can move up or down under defined rules. They can look attractive in falling markets, but they need more attention than a simple fixed deal.

Before choosing a tracker, read how often it updates, whether there are caps or floors, and what fees apply. If you prefer set-and-forget budgeting, a competitive fixed tariff is usually simpler. If you are comfortable monitoring the market, a transparent tracker can be part of a deliberate strategy.

Time-of-use, Economy 7 and EV tariffs are related but different: they price energy cheaper at certain times of day. They work best if you can shift usage (overnight charging, delayed appliances). Confirm your meter type before switching to one.

Green tariffs and what “100% renewable” means

Many deals offer 100% renewable electricity, sometimes with green gas options. Marketing language varies. Use Brillia’s green energy filter on results, then read the deal details for what is included and any certification claims the supplier makes.

Green pricing is not automatically more expensive than brown power on every deal — compare estimated annual cost the same way you would for any other tariff. If sustainability is a priority, filter first, then sort by cost so you are not paying a large premium for a similar product.

Dual fuel vs single fuel

Dual fuel means gas and electricity with one supplier — often simpler paperwork and one Direct Debit. Electricity-only or gas-only comparisons make sense if you heat with electricity only, use communal heating, or have a separate arrangement for one fuel.

When you compare on Brillia, pick the fuel type that matches what you intend to switch. Mixing assumptions (for example, entering dual-fuel usage but only planning to move electricity) will distort estimated savings.

Standing charges, unit rates and “cheapest” claims

Marketing often highlights a low unit rate. For low-usage homes, standing charges can dominate. For high-usage homes, unit rates matter more. Estimated annual cost folds both together for the usage you enter.

Exit fees, warm-home discounts eligibility, and payment method premiums can still change the real-world outcome. Treat comparison results as a shortlist, then read the deal page before you apply.

Ofgem licensing means suppliers must follow industry rules, but products still differ. If something looks too good to be true, check the term length, exit fee and payment requirements — or ask us before you proceed.

How to choose a tariff type in practice

Start with how you pay and your risk tolerance. Want certainty for a year? Shortlist fixed deals with acceptable exit fees. Coming off a fixed soon? Compare before SVT roll-over. Happy to watch the market? Consider trackers with clear rules.

Then look at estimated annual cost for your usage, not just unit rates. Check standing charges, exit fees, contract length and any smart-meter requirements. Our deals results let you sort by cheapest, biggest saving, top rated or green — see how Brillia works for the full flow.

For habits that reduce kWh after you have a better tariff, read how to save on energy bills. More guides live on the guides page, and you can always contact us with a specific tariff question.

Frequently asked questions