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10 Dec 2020

Top five cheapest energy deals for December 2020: why your energy bill can increase when you're on a fixed tariff

Avro Energy, Green, Outfox the Market, Shell Energy and Simplicity Energy are selling the cheapest gas and electricity deals right now
House with lights on inside surrounded by snow

Over £200 of savings could be yours by switching to one of the current cheapest energy tariffs, even while you're turning up the heating to beat the December chill.

If you have gas central heating, you'll use most of your gas during the winter months. Decorating your house with Christmas lights, slow-cooking comfort food and curling up with box sets on chilly evenings all increase your energy use at this time of year too. So being on a good value energy deal is crucial.

Being told that your gas and electricity bill is increasing even when you're on a fixed deal is a regular question we come across. Find out why this happens and what you can do about it below the table.

Read on to see the cheapest deal for you, or compare gas and electricity prices using Which? Switch, our independent energy comparison website.

You can also phone us on 0800 410 1149 or 01259 220235.

Top five cheapest gas and electricity deals

You could save more than £180 over a year by switching to any of the cheapest tariffs listed below. That's assuming that you're currently on a tariff that costs the maximum permitted by the price cap and based on a home using a medium amount of gas and electricity. It's also based on paying by monthly direct debit.

How much you pay for energy and the exact amount you could save by switching depends on how much gas and electricity your home and family use. Prices also vary by region.

CompanyTariffAnnual price (medium user)Fixed/ variableExit feeSavings compared with price cap
1Outfox the MarketFix'd 20 19.0 - paperless£821FixedNone£221
2Simplicity Energy2020 Cabbage - paperless£823Fixed£35 per fuel£219
3GreenAspen - paperless£851Variablen/a£191
4Avro EnergySimple and Superprime - paperless£855FixedNone£187
5Shell EnergyEnergy February 2022 v4 - paperless£857Fixed£30 per fuel until 10th Jan 2022£185

Prices are based on widely available dual-fuel tariffs for a medium user (Using Ofgem averages of 12,000kWh gas and 2,900kWh electricity), paying by fixed monthly direct debit with paperless bills. Prices are averages across regions, rounded to the nearest whole pound and correct on 8 December 2020. Simplicity Energy's deal is not available in north Scotland.

The current cheapest deal, from Outfox the Market, has no exit fees so you're free to switch again whenever you wish. The same applies to the tariffs from Avro Energy and Green.

But you'd have to pay £70 to move to another deal or supplier if you wanted to leave Simplicity Energy's year-long 2020 Cabbage tariff early. The exit fees are slightly less on Shell Energy's tariff and it's a longer fixed deal - lasting until February 2022.

Exit fees don't apply in the last 49 days of your fixed tariff so you can arrange to switch penalty-free when it's coming to an end.

Variable deals never have exit fees.

Three of this month's cheapest tariffs come from suppliers included in our most recent energy companies' satisfaction survey. Find out what customers thought of Avro Energy, Outfox the Market and Shell Energy.

woman on the phone looking at an energy bill
Why has my energy bill increased when I'm on a fixed deal?

Signing up for a fixed tariff guarantees that the rates you pay won't change for the length of the contract (often 12 or 24 months). But this doesn't mean that the amount you pay by direct debit can't change.

We often get queries about this. The first thing to note is that it's the daily standing charge and unit rate (the two elements that make up most energy tariffs) which are fixed, not the amount you pay each month.

Standing charge - a daily amount payable regardless of whether or not you use any gas or electricity.

Unit rate - the price of a kilowatt hour of gas or electricity.

If you signed up to a fixed deal and your supplier has told you it plans to increase your direct debit payments, consider the following:

  • Have you used more gas or electricity than expected? When you switch, you're usually asked to supply your last year's usage. Your supplier bases your direct debit payments on this. If you use more than last year, your direct debit payments may increase.
  • If you didn't provide your usage then the energy firm will base your payment on an average household of a similar size. If your usage is more than the prediction then your payments may increase.
  • Are you coming to the end of your fixed deal? If you don't switch then you'll move automatically onto your energy firm's default or out-of-contract tariff. These are often pricier and can be the maximum permitted by the price cap. Taking this into account can lead to direct debit increases.
  • Does your tariff come with seasonal payments? Some energy firms apply a 'winter uplift' or 'winter weighting' to customers' direct debit payments in the colder months.

Woman sitting at a laptop frustrated
If you disagree with your direct debit increase, you can challenge it with your supplier. First check whether your account is in credit and whether your current payments are likely to cover your annual usage (look at your online account or latest annual statement for this). Some firms let you alter your direct debit in your online account.

Your energy supplier must tell you in advance if it plans to change your payments (often 10 working days), according to the direct debit guarantee.

Some firms will let you opt-out of seasonal payments if you ask.

Read more about getting the best energy deal.

Which? energy pricing research

Prices are based on widely available dual-fuel tariffs, paying by fixed monthly direct debit, with paperless bills. Energy use is based on Ofgem's annual average figures for a medium user (12,000kWh gas and 2,900kWh electricity).

Data is from Energylinx. Prices given are averages across regions, rounded to the nearest whole pound and correct on 8 December 2020.