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Extracted Energy from Fuel

For combustible fuels the fuel prices on the home page of this site and in the fuels page indicate the price per kWh of the fuels if burned at close to 100% efficiency. They indicate the maximum extractable, 'locked up', chemical energy within the fuels. No equipment (boiler or fire) burns the fuel with 100% efficiency. So the actual cost per kWh is always higher. This is indicated on many of the pages on this site, showing for example the difference between a modern boiler and an old inefficient boiler.

The table below presents all the main combustible fuels in the UK their 100% price per kWh and efficiencies down to 10%. The shaded areas of the table give some typical examples of equipment and their efficiencies. It is worth taking note of this in for example a decision to replace an old boiler, long term it may be more cost effective than you think.



Fuel Type Effective price (pence) per kWh of delivered energy
taking into account the efficiency of the unit burning the fuel.
Prices last updated 21th April 2021

100%
95%
90%
85%
80%
75%
70%
60%
50%
40%
30%
20%
10%
Gas
3.9 4.1 4.3 4.6 4.9 5.2 5.6 6.5 7.8 9.8 13 19.5 39
Heating Oil (Kerosene)
4.4 4.6 4.9 5.2 5.5 5.9 6.3 7.3 8.8 11 14.7 22 44
Bulk LPG
7 7.4 7.8 8.2 8.8 9.3 10 11.7 14 17.5 23.3 35 70
Typical fully condensing modern boiler Typical of an older inefficient boiler
Wood Chip
3.7 3.9 4.1 4.4 4.6 4.9 5.3 6.2 7.4 9.3 12.3 18.5 37
Wood Pellet
5.5 5.8 6.1 6.5 6.9 7.3 7.9 9.2 11 13.8 18.3 27.5 55
Wood Log
8.3 8.7 9.2 9.8 10.4 11.1 11.9 13.8 16.6 20.8 27.7 41.5 83
Coal
2.6 2.7 2.9 3.1 3.3 3.5 3.7 4.3 5.2 6.5 8.7 13 26
Smokeless Coal
6.3 6.6 7 7.4 7.9 8.4 9 10.5 12.6 15.8 21 31.5 63
Typical modern stove Typical open Fire
Butane 4.5kg cylinder
29.7 31.3 33 34.9 37.1 39.6 42.4 49.5 59.4 74.3 99 148.5 297
Butane 7kg cylinder
26.1 27.5 29 30.7 32.6 34.8 37.3 43.5 52.2 65.3 87 130.5 261
Butane 15kg cylinder
19.5 20.5 21.7 22.9 24.4 26 27.9 32.5 39 48.8 65 97.5 195
Propane 3.9kg cylinder
32.8 34.5 36.4 38.6 41 43.7 46.9 54.7 65.6 82 109.3 164 328
Propane 6 kg cylinder
27.6 29.1 30.7 32.5 34.5 36.8 39.4 46 55.2 69 92 138 276
Propane 13kg cylinder
16.4 17.3 18.2 19.3 20.5 21.9 23.4 27.3 32.8 41 54.7 82 164
Propane 19kg cylinder
13.4 14.1 14.9 15.8 16.8 17.9 19.1 22.3 26.8 33.5 44.7 67 134
Propane 47kg cylinder
11.6 12.2 12.9 13.6 14.5 15.5 16.6 19.3 23.2 29 38.7 58 116

Of the many questions from users of this site, the most common one is simply why are my bills so expensive and the questions often come from people in rented accommodation. The reasons in this type of accommodation are often the same, lack of investment in insulation and modern boilers by landlords. The table clearly shows the effect installing modern equipment on your energy bills, but how do you persuade the landlord!

The inefficiency of open fires was a great surprise to me when I first investigated this 5 years ago. It is well worth considering a modern stove as an alternative if you can afford the installation cost.

Price Trends

The below graphs gives the price trend for a unit (kWh) of Gas and Electricity from 2007. The data is from official UK government sources and is a Great Britain average. As you can see the price has gone up a lot in just 6 years with no sign of slowing down.

Comments and Questions

The ability to post comments and questions has be temporarily suspended, owing to large volumes of spam, for now please direct messages to us on twitter instead (at the top of the article there is a button). A solution is being sought.

Extracted Energy From Fuel - Appliance Efficiency - Katy  2014-08-04 14:49:30
Hi,

Could you please tell me whether many households would use gas/oil boilers of less than 50% efficiency? Do you have an estimate of the average boiler efficiency for the UK?

Also, there seems to be a large variance in efficiency of open fires. Do many open fires actually reduce to as little as 20% efficient?

Thank you
here is a link - rdh  2014-08-17 18:42:41
https://www.gov.uk/government/statistics/quarterly-energy-prices-june-2014
reply - rdh  2014-08-17 18:19:26
Sorry Katy
I missed this question, they can get buried under a metaphorical pile of e-mails.
I'm afraid I do not have that info. Have you looked at the UK Gov Websites do you have their documents. I would guess that very few are that bad anymore, most would have moved on to new boilers by now.
The old EAGA partnership would have know that, I think they are closed down now.
Open fires, coal wood etc, are very inefficient, most of the heat going up the chimney. Stoves are much more efficient, but much more expensive.
Cheers
Richard