Gas V Electric heating, some math work

Strider590

Firstly im new here, so please do forgive me if im repeating something thats been posted elsewhere!

I currently live alone in a 3 bedroom house (more like 2+box room), the intention was to rent a room out but the place is too messy just now.
Im using British Gas for my Gas/Elec and ive wondered for quite some time whether it's cheaper to heat one or two rooms with oil filled radiators than it is to heat the whole house on the Gas central heating.
For example, I wake at 4:30am to be at work for 6am. It seems a waste to use the CH just before I go to work, but i DO need some heat else I just can't get out of bed :rotfl:

Yesterday I checked my gas meter (imperial) just before turning on the CH, after one hour id used 0.4units of gas, which works out to around 45p (using the tier 2 price).
Now using a oil filled radiator in one room, set to 1kw for 1 hour I used (obviously) 1kwh, which equals 9p (again using the tier 2 price).

I've done a very nice excel spreadsheet that does these calculations for me and proven its accuracy by checking my quarterly bill. (accurate to within £2 a quarter).
Ive used the "gas units used x 2.83 (metric conversion factor) x 1.0226400 (volume conversion factor) x 39.3535 (calorific value) / 3.6 (kilowatt hour conversion factor) = kilowatt hours" formula.

Have I gone horribly wrong or is it really cheaper to use the oil filled radiators to heat 2 rooms (bedroom and computer/tv room) rather than the whole house on gas CH? I pretty much assumed that the CH was cheaper, but logic and math is telling me different.

If my theory is correct, id like to use the CH maybe once per day unless I have visitors and turn the thermostat down to 18-19c.

Cardew

Strider590 wrote: »

IIm using British Gas for my Gas/Elec and ive wondered for quite some time whether it's cheaper to heat one or two rooms with oil filled radiators than it is to heat the whole house on the Gas central heating.

Welcome to the forum.

Variations of your question have been posed several times.

You are comparing 'apples with lemons' in that you are comparing the cost of "heating the whole house" with the cost of 2 rooms.

Surely you don't have to heat "the whole house" you can simply turn off the radiators in the rooms you are not using and just have the CH heat 2 rooms?

Or you could buy a CH programmer that can control different zones in a house

On your figures, you obviously have an imperial gas meter(1 unit = 100 cubic feet) and 0.4 of gas unit is approx 12.5kWh. So as you price that at 45p that puts tier 2 gas at 3.6p/kWh.

The only fair comparison is to price gas against electricity and you would need to know the efficiency of your boiler - which can range between say 50% for an antique to 90% for a modern condensing boiler. So 4p to 7p/kWh

Incidentally, you say you are with BG. Are you sure you have the prices correct? electricity seems low at 9p. Or are you on an old capped tariff in which case gas seems high!

Strider590

According to my online billing:

Gas
From 30 Jul 2008 to 17 Oct 2008
For standard Gas registers, 7.115 pence per kilowatt for the first 7.342 kilowatts used a day, and 3.561 pence per kilowatt for the rest.

Electric
From 30 Jul 2008 to 17 Oct 2008
For standard Electricity registers, 20.170 pence per kilowatt for the first 1.37 kilowatts used a day, and 9.404 pence per kilowatt for the rest.

Strider590

Oh and I hadn't tried turning the other radiators off.... Does it really make a big difference? A couple of my rad thermostats are broken, but I might be inclined to heat the ground floor on the CH so that its bareable and of course heat rises up through the floorboards so I could top it off with an electric radiator where needed. I just want to find that perfect balance, to leave the house comfortable yet cost as little as possible.