Electricity Suppliers’ Fuel Mix 2013

Posted in Green on December 30th, 2013 by Andy
Wind turbines silhouetted against a sunset

How much of an effect do these things really have?

How clean is UK electricity really? How much cleaner is the supply from a “green” electricity company? Will switching to electric cars mean less pollution?

All these questions depend on the fuel mix of the electricity supply. The power plants operated by some power companies are much dirtier than others, and by law all companies are required to declare where they’re getting the juice they sell you. The list below is an updated version of the one I compiled last year.

SupplierNuclearGasCoalRenewOtherCO2 intensityCO2 emissionsCost on billExternal costCost including external
British Gas28%34%26%10%2%0.3791,251£521.21£59.32£580.53
Southern / Scottish Hydro / Swalec / Atlantic / M&S /Ebico1%28%54%15%2%0.6132,023£534.81£104.26£639.07
Scottish Power1%26%59%13%1%0.6402,112£531.99£111.27£643.26
Good Energy0%0%0%100%0%0.0000£533.72£1.82£535.54
Utility Warehouse0%51%34%14%1%0.5121,690£558.58£68.75£627.33
First Utility5%31%52%8%4%0.4701,551£581.42£106.03£687.45
Green Energy UK0%79%0%21%0%0.190627£498.96£10.55£509.51
Spark Energy5%31%52%8%4%0.6192,043£492.33£106.03£598.36


The supplier’s standard tariff was used, and does not take into account any discounts or special offers.

External costs are (in pence per kWh): coal = 5.4, gas = 0.39, nuclear = 0.48, renewable = 0.055, other = 6.05. (source: Pearce et al 1992). Fuel mix multiplied by this number gives the external cost, and the annual total shown above is for 3300kWh.

The Big Six

Between them Npower, British Gas, EDF, EON, SSE and Scottish Power supply 90% of homes in the UK, so the power they’re generating is the most important.

  • Npower: Once again, one of the worst suppliers. They manage to combine high prices with a supply that has actually got dirtier recently. Avoid.
  • British Gas: Rising prices and a somewhat less clean supply than last year has eaten into their lead over the other Big 6, but they’re still the best overall.
  • EDF: Snapping at BG’s heels comes EDF. They’re slightly more expensive but the carbon intensity of the power they feed into the gird has dropped even further, and they’re now the cleanest generator among the Big 6 by a long way. At 0.161kg CO2e kWh-1 they now supply genuinely low-carbon electricity to 5.7 million households. If you want a Big 6 supplier, you could do far worse.
  • EON: Their use of coal has leapt from 30% to 50% in the last year, and the numbers reflect it. Cheap, but definitely a generator that’s heading in the wrong direction.
  • SSE: The biggest supplier of renewable power to the grid is also one of the burners of coal, which erases all the good work on renewables.  Their coal use has also leapt this year, from 35% to 54%, which represents a huge amount of coal burned. Don’t buy your power from here if you like living on Earth.
  • Scottish Power: Saving the worst for last, Scottish Power claims the wooden spoon from Npower this year. Despite supplying good amounts of renewable power their heavy reliance on coal over gas makes them the dirtiest supplier on the grid.

Smaller suppliers

The big winner this year is Green Energy UK, who combine seriously low prices with the second cleanest fuel mix (base on natural gas an renewables). Only the 100% renewable Good Energy beat them on external cost, but can’t match their prices. Other honourable mentions go to LOCO2 and Ecotricity, both of which manage to beat all of the Big 6 on price and green credentials.

Less impressive are Spark Energy, who are cheap but very dirty, and First Utility who once again claim the dubious honour of being the worst supplier in Britain. If I was one of their customers I would really want to know why they seem to pay so much for the dirtiest power available, when it should be the cheapest.

Ovo’s performance looks pretty lacklustre, but like Ecotricity and Green Energy Uk they also have a 100% green tariff that would be well worth a look.

What is the “external cost”?

It’s an attempt to sum up all the different negative impacts that generating energy has, from carbon emissions and deaths from poor air quality, to destruction of forests due to acid rain. It expresses this impact as a cost in pence per kWh generated. In a fair world, the source of that damage (ie: the owner of the power plant and their customers) would pay for that damage, so by adding the external cost to the actual cost of  your power you can get an idea of whether cheap dirty power is a better deal for society than expensive clean power.

If you’re feeling really keen to offset this you could of course make a donation to a green project equal to your external cost.  Or you could sink it into a green crowdfunding project like the ones on Abundance Generation. Just a thought.

Pearce, D.W., Bann, C. and Georgiou, S. (1992) The Social Costs of Fuel Cycles, Report to 
the UK Department of Energy,
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