Choosing an energy tariff can feel overwhelming. Fixed, variable, time-of-use, smart… It’s not always clear what the difference is — or which one actually saves you money.
The good news? Once you understand how each tariff works, the decision becomes much simpler.
In the UK, energy tariffs fall into three main categories recognised by Ofgem.
Let’s break them down clearly and practically — so you can decide what works best for your home, lifestyle, and budget.
If you’ve never switched, or your fixed deal ended and you didn’t choose a new one, you’re probably on a Standard Variable Tariff (SVT).
The price cap limits the rate per unit, not your total bill. If you use more energy, you pay more.
Best for: Short-term flexibility, not long-term savings certainty.
A fixed-rate tariff locks in your energy prices for a set period, usually 12 to 24 months.
Under certain rules from Ofgem, suppliers can move you onto another fixed deal at the end of your term — as long as it’s no more expensive than the SVT and has no exit fee.
Best for: Households who want predictable bills and peace of mind.
Most UK households are effectively on a flat-rate electricity tariff.
According to research from Nesta, around 91% of GB households remain on flat-rate pricing.
Best for: Simplicity.
Time-of-use tariffs are part of the new wave of smart energy pricing.
Research from Nesta shows around 9% of households now use time-of-use electricity tariffs — and that number is growing.
You’re more likely to save if you have:
Nesta-commissioned research suggests heat pump owners could save up to around £600 per year by moving from a standard tariff to a time-of-use tariff — even without optimising usage perfectly.
If most of your usage happens at peak times and you can’t shift it, your bills could increase.
Best for: Homes with flexible, shiftable electricity demand.
Block tariffs charge different rates depending on how much energy you use.
For example:
They’re uncommon today and used by only a small minority of households, according to Nesta.
Best for: Very specific usage patterns — rarely the mainstream choice.
| Tariff Type | Price Changes? | Flexibility | Best For |
|---|---|---|---|
| Standard Variable | Yes (within price cap) | High | Short-term flexibility |
| Fixed-Rate | No (during term) | Medium (exit fees possible) | Budget certainty |
| Flat-Rate | Same price all day | High | Simplicity |
| Time-of-Use | Cheaper off-peak, dearer peak | Medium | EV/heat pump homes |
| Block Tariff | Changes by usage level | Low–Medium | Niche cases |
Instead of asking “Which tariff is cheapest?”, ask:
If you're considering:
A time-of-use tariff may become far more attractive in the future.
Some homeowners enjoy optimising their energy usage. Others prefer “set and forget.”
Choose a tariff that matches your lifestyle — not just headline savings.
Even once you understand tariff types, comparing deals can still feel time-consuming.
Rates change. Exit fees vary. Standing charges differ by region. And it’s not always obvious which tariff genuinely works best for your home.
That’s where a Switch Together energy switch can help.
Switch Together runs group energy switching schemes in partnership with councils and community organisations across the UK.
Instead of you comparing dozens of tariffs on your own, Switch Together:
You stay in control the whole time — there’s no obligation to switch.
If your home has both solar panels and a heat pump, your energy setup is very different from the “typical household” used in national averages.
You’re generating electricity.
You’re using more electricity (because you’re heating your home with it).
And you have more flexibility than most.
That changes which tariff makes sense.
Heat pumps run on electricity rather than gas. That means your electricity consumption is higher than the UK average — especially in winter.
Because of that:
Your solar panels generate most of their electricity during daylight hours — often when grid electricity isn’t at its cheapest.
In summer, you may:
In winter, however:
This seasonal mismatch is key when choosing a tariff.
If you prefer predictable bills and don’t want to think about timing your usage, a fixed tariff offers certainty.
Best for:
But it won’t reward you for shifting usage.
This is where things get interesting. Because heat pumps can be:
Research highlighted by Nesta suggests heat pump owners could save significantly by moving from a standard tariff to a time-of-use tariff — even before fully optimising usage.
You benefit most if you:
However:
If you generate surplus solar electricity, your export rate matters too.
While the standard import tariff determines what you pay for electricity, your export tariff determines what you’re paid for surplus generation.
Some time-of-use import tariffs pair well with competitive export rates — but not always. It’s important to look at both sides together.
Instead of asking:
“What’s the cheapest tariff?”
Ask:
For many solar + heat pump households: