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
|Heating Oil (Kerosene)
|Typical fully condensing modern boiler||Typical of an older inefficient boiler|
|Typical modern stove||Typical open Fire|
|Butane 4.5kg cylinder
|Butane 7kg cylinder
|Butane 15kg cylinder
|Propane 3.9kg cylinder
|Propane 6 kg cylinder
|Propane 13kg cylinder
|Propane 19kg cylinder
|Propane 47kg cylinder
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.
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.