Am I calculating the cost of heating by propane right?

[tinnews]

We live in a rural location and inherited a central heating system which runs on propane delivered by Shell to a large tank in the garden.

I'm considering the alternatives and, as part of this exercise, have calculated what I think the propane costs per kwH.

It's about 35p/litre at the moment and the calorific value I have found is about 7kwH per litre. So this gives a cost of something around 5p per kwH.

Presumably however this is before boiler efficiency is taken into account so, given that it's an old boiler (a Potterton NetaHeat) I guess that is somewhere around 50% - or is it even worse than that?

So my hot water and heating by gas is costing something like 10p per kwH or even more - eek. We'll use the overnight electricity at around

3p/kwH even more then!

[Michael Chare]

I would have thought that the old boiler was atleast 70% efficient.

In part it does depend how you treat the waste heat. If the boiler is say in the kitchen, then likely part of the waste heat is keeping the kitchen warm rather than going up the chimney.

I use 28 sec heating oil. At a nominal calorific value of 19,600 Btu/lb which I make 10.57 kwh/L this works out at 2.83 pence/kwh at 30p /litre. My new non condensing boiler has a claimed efficiency of 85.1% which gives a price per kwh of 3.335 p/kwh which is just less that the 3.393 p/kwh I am now paying for off peak electricity! Of course there are pipe wok losses.

When I last did this calculation oil was 15p/litre!

Have you considered one of those heat pump solutions that gets the heat out of the ground?

I am not a fan of propane, even for cooking out induction hob is at least as good, and certainly saver than gas.

My neighbour arranges the heating oil for a number of us. He just uses who ever is the cheapest supplier at the time.

[Ian Stirling]

I'm in the middle of a 'my heating bills are too high AAARRGH' excersize.

YHMV of course.

First, go round the entire structure, and find out the actual composition of everything. Now, work out the heat losses through walls, windows, floors, roof, and any other.

Depending on how much DIY you are willing to do, you can then get on with considering various alternatives. Insulation varies from around 2 pounds a square meter (rockwool, 100mm) to 12 pounds a square meter, for 100mm kingspan.

It turned out that in total, to insulate my 110m^2 of walls, I needed as the cheapest way, several sheets of kingspan (to do round the 50cm deep windows, and to avoid having to cut in too deeply(diamond angle grinder

+SDS)) about 10 rolls of rockwool, and about 40 sheets of plasterboard, and 20 rolls of kitchen foil.

I could also have spent about 300 quid on wood to put this together, but am reclaiming most from the wood ripped out - it would be faster to do it the other way.

The total will come in substantially under a grand, and will pay back in

3 winters (including this one).

This takes the walls to current standards - in my case from an average of around 3Kw heat departing from the walls, down to 400W. Much more is diminishing returns.

Attic of course is cheapest, if uninsulated, but you're probably not that lucky. Consider payback times on everything, after actually calculating the heat losses. My first instinct would have been to replace the windows with double glazed units, after manufacturing new window tops. However, actual calculation revealed that the windows lose well under a quarter of the heat. Less with curtains closed.

[tinnews]

It's a balanced flue so the only waste heat not lost is anything that comes through the case.

We have lots of wood and already have a big wood burning stove and are considering a second one.

We will continue to use it for cooking as our panware is too varied to manage with an induction hob.

[tinnews]

I was more interested in seeing the relative costs of propane and electricity. I just want to confirm my calculations which suggest that electricity is very little different in cost from propane even at peak rates. Thus simply not using our gas central heating, using our wood burners more (we have lots of our own wood) and topping up with electric heating will save us money.

I agree with your insulation approach, that's going to save money (assuming current insulation is poor) regardless of what fuel is being used.

[PeterK]

Are you paying a competitive price. I pay just under 26p/l. The average price of lpg for road use is 39.9 p/l and that includes duty of 7.82p/l + VAT at 17.5%. Time to switch? see the documents at

.I don't know if the "order" implementing the recommendations has been made but the suppliers know what is coming.

PeterK

[Ed Sirett]

In fact it has a fanned flue with electronic ignition so it is towards the better end of the non-condensing spectrum. In fact for it era it was exceptional. Probably has SEDBUK of around 75-80%

[tinnews]

Yes, sorry, you're quite right. I was just trying to say that it hasn't got a big diameter pipe coming out of the top of it.

The efficiency surprises me, I didn't realise that gas boilers of that vintage were so good. Anyway it doesn't affect my calculations all

*that* much, it's still much cheaper to use electricity overnight to heat our water and it's a toss-up during the day between electtricity and gas for heating.

[Ed Sirett]

They generally weren't but that model was. Although it's flue pipe and terminal are unique they were much smaller than the massive flues and terminals of their contemporaries.