I must have worked this out wrongly!

Wibbleone

We have not been using our gas CH recently, instead we have been heating an individual room with a 1Kw electric heater to save money.

I thought I’d check what savings we were making and got a bit of a shock (or I have worked it out wrongly!) as the gas CG costs less than the single room electric heater.

Our supplier (British Gas – The People’s Tariff) charges us 28.408p per unit (KWH) for electric & 7.476p per unit of gas. I found that one unit of gas = 11.3627KWh.

The 1Kw electric room heater costs £0.28/hour to run.

I checked the gas boiler manual (Ideal Logic Combi C30) and found it uses 0.627M³ of gas per hour running the central heating.  So, if we are paying £0.07 per cubic metre of gas, the boiler, heating the whole house, must cost £0.07 x 0.627 or £0.04 per hour.

It seems crazy that the whole house can be heated for seven hours for about the same cost as heating a single room electrically.

Have I made a mistake? 

Benny2020

Its not 7p for m3 its 7p for a kwh of gas, and electricity is 4 times more expensive per kwh than gas.
Your central heating costs around 11.2 times more than your figures.

stewie_griffin

Yes you have. 0.627 of a unit works out at about 53p by my calculations. It's around 7kWh of gas multiplied by your unit price.

pochase

Wibbleone said:

We have not been using our gas CH recently, instead we have been heating an individual room with a 1Kw electric heater to save money.

I thought I’d check what savings we were making and got a bit of a shock (or I have worked it out wrongly!) as the gas CG costs less than the single room electric heater.

Our supplier (British Gas – The People’s Tariff) charges us 28.408p per unit (KWH) for electric & 7.476p per unit of gas. I found that one unit of gas = 11.3627KWh.

The 1Kw electric room heater costs £0.28/hour to run.

I checked the gas boiler manual (Ideal Logic Combi C30) and found it uses 0.627M³ of gas per hour running the central heating.  So, if we are paying £0.07 per cubic metre of gas, the boiler, heating the whole house, must cost £0.07 x 0.627 or £0.04 per hour.

It seems crazy that the whole house can be heated for seven hours for about the same cost as heating a single room electrically.

Have I made a mistake? 

Your mistake is that M3 is not the same as KWh. There is a complex formula, but if you multiply the m3 by 11.2 it is near enough. You even mention it, but you forgot to integrate into your formula.

So if you use you would need to multiply the 0.627 by 11.2 = 7.02KWh. Multiply by the 7.476 and you get to 52.50p.

Second mistake is that your boiler will not run the whole time. It will use a lot when it heats up, but thereafter it will just hold the temperature and the hourly cost is much lower than the 50p.

So you will still end up that  heating with electricity is so much more expensive that  your statement  

It seems crazy that the whole house can be heated for seven hours for about the same cost as heating a single room electrically.

is almost true again.

Gerry1

Wibbleone said:

Our supplier (British Gas – The People’s Tariff) charges us 28.408p per unit (KWH) for electric & 7.476p per unit of gas. I found that one unit of gas = 11.3627KWh.

I checked the gas boiler manual (Ideal Logic Combi C30) and found it uses 0.627M³ of gas per hour running the central heating.  So, if we are paying £0.07 per cubic metre of gas, the boiler, heating the whole house, must cost £0.07 x 0.627 or £0.04 per hour.

Have I made a mistake?

Yes, you have made two mistakes.

• You are billed for gas usage in kWh, as your bill will show.

• The boiler will not always use 0.627M³.  It will modulate or switch off and on when the desired temperature has been reached.  You would need to read the meter on the wall and convert the volume to kWh to get an accurate cost (which will also include hot water).

However, you are correct in that an electricity kWh costs about four times that of gas.  It's probably cheaper to use gas, but remember to turn down the radiators in the rooms you are not using.

Wibbleone

Thanks everyone.  I see my mistake.  Mixing cubic metres of gas with KWh. 
I looked again at the boiler manual and it says it uses 6.7Kw per hour. So that's £0.07 x 6.7 = £0.47/hour to run, but like pochase said, the boiler will initially run flat out to bring the CH to temperature then run far lower for the rest of the hour maintaining the temperature.

All in all, it seems that heating one room electrically will end up costing the same as the whole house with gas.

Benny2020

How much is a cubic metre of electricity?

Wibbleone

well, someone had to say it!