comparing the cost of fuels for heating

I am the person who wants to know if using an electric fan heater in one room costs less than heating the whole house using gas*. At parties I can keep a sofa to myself just by asking that question – but I think at last I’ve found a website to share the sofa with. Called Confused about energy the website answers better questions about energy and it has this excellent graph. The information I’ve gleaned is more useful than many official sources, and indeed any source.

*I may be better off using a fan heater rather than heat the whole house: compare the cost of electricity (100% efficient) with the cost of gas central heating (90% efficient). Rounding up prices, the 2kW fan heater will cost 2 * 20p an hour = 40p and a 25kW boiler will cost 25 * 5p * 90% for an hour = 140p.

Look at it like this, writes my colleague Nicola: “a rough rule of thumb is that as electricity costs three times the cost of gas, you are better off fan heating a room if the room is less than 1/3 of the space of the house.

We can assume the heating runs continuously and no thermostat will switch off either form of heating. If it does the cost per hour is lower but the comparison is still valid. (By the way, my boiler runs for 60% of the time – averaged over two years of operation. I don’t know what percentage of time a fan heater runs for).

Credit: in a new tab)

This bar graph speaks for itself but I’ll add my observations:

  • This is about money not impact on the world. If you can forage for wood, that’s the cheapest fuel. Dressing warm or feeling cold is greener.
  • Heating oil is only 25% more expensive than gas, but it’s a third of the price of electricity which is a wrong way to do heating.
  • Cooking on a gas hob is a minor use of fuel. To save energy, focus on the use of the 3kW oven.
  • Calor gas heaters (with a gas bottle inside them) cost more to run than an electric fire. And I had always imagined these gave value.
  • If you thought that natural gas (methane) was best value – coal is even cheaper, and even cheaper than wood. The roadside sellers (‘logs for sale’) have their own ideas about the price of that. If you do see wood on sale compare its price with coal at £7.50 per 25kg trebles. Wood offers about half (~ 56%) the kWh of coal.
  • Coal evil coal is not quite this cheap at figures for 2019. It costs £300 for 1000kg coal valued at 7kWh per kg. The coal costs £0.30 per kg divided by 7 making 4.3p per kWh.
Sorted subset of the above bar graph.

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