I have oil-fired central heating on a sealed system whereby I can program CH and DHW separately. I also have Economy 7 dual rate electricity, and it has been my practice to use the oil for both CH and DHW. With the recent increases in oil price, I'm wondering whether to use the immerser on cheap rate for DHW. The problem is I suspect the element is faulty. When I switch on the immersion heater, my energy monitor shows an increase. Can I assume from this that it is actually heating the water?
True enough but if the OP is worried about oil consumption the space heating is what will be gobbling it up. In the sumer we use about
25l/week for HW. The recent cold period has had consumption at
25l/day...
And turn the HW heating from the boiler off... Remember the immersion is only 2 or 3kW, the boiler may well be 10 times that. If all things were equal the immersion could take 10 times longer to heat the cylinder than the boiler.
Also the OP syas he has E7, using that to heat the cylinder during the off peak (cheap) period may well be cheaper than the oil boiler. If you are paying 50p/l for oil that is very roughly 5p/kWHr, when you take into account boiler effcieny etc it's probably more like
6p/kWhr of electricty equivalent.
Note that a decent E7 cylinder will have two immersions, one near the bottom that is only powered during the off peak times and will heat the whole cylinder. And one near the top that can be powered at anytime via a "boost" button on the E7 immersion controller, this will only heat the top section of the cylinder.
I gather the calorific value of heating oil is around 43 MJ/kg and its density is some 0.83 kg/l, so we get about 36 MJ/l which is 10 kWh/l.
The cost per kWh is therefore 6.6p. An oil fired boiler is not going to be hugely efficient. Say 80% if you're lucky, which would come to 8.25p per useful kWh.
That's cheaper than daytime electricity, but more expensive than off-peak. Until that goes up in price too. :-(
Electricity is ever more expensive to produce than oil, gas etc, simply because its made from those fuels via lots of industrial plant. E7 changes the picture because its a - there's a term for it I cant think of, but a price offer based on the extra costs of generating it rather than the whole system costs. Ie its mainly the daytime users that pay for the plant, distribution, etc.
Ouch. I am so glad I have gas, a well insulated house and that I am often out at work in the daytime. Obviously I am not so glad that they have f***** up by billing but I'll get that money back after I have phoned them and given them a good bollocking.
Yes, good point..
It seems that we have come full circle and we are back to the "Worth it to have Economy 7?" thread that I suggest the OP reads.
That's an oversimplification. Of the various methods used to generate electricity, burning oil is probably one of the more expensive and less common. Also don't forget that all this industrial plant introduces economies of scale. It has got to be more efficient in terms of fuel consumption --even if we were only using oil and no other fuel-- to burn it centrally in one muckle industrial furnace and distribute the energy as electricity than to distribute the oil and burn it in individual domestic boilers, especially if you need the electricity distribution infrastructure anyway for purposes other than heating. In theory therefore electric heating ought to be cheaper than oil-fired boilers, especially if you factor in the cost of installing and maintaining the boilers.
Unfortunately energy companies are businesses, and exist to make money. They don't charge according to cost, but according to market forces.
I think the term you're looking for is marginal cost. But even that doesn't quite explain it. It may be possible to run the industrial plant more efficiently if you vary the "volume control" less during the daily cycle, so it can make more sense to sell off-peak power even at *below* marginal cost than not to generate it in the first place.
The burn may well be more efficient but then you have to add in the losses resulting from converting the heat into electricity. The laws of thermodynamics mean that this is quite significant even with the most efficient turbines.
Sure, but the alternative losses are also pretty big. You have to fuel the tankers to deliver the oil to households. You have to build and maintain those tankers, and pay the drivers. You have to build, install, and maintain the household storage tank and boiler. And you're still lucky if 80% of the energy in the delivered oil ends up inside the house.
Coal powered Drax is getting pretty close to 40% once changes are complete. Other power stations can and do exceed that figure (think gas is somewhat higher).
Economy 7 is cheaper because night time demand is lower, even though a lot of heavy industry is gone (who got shafted one by one by the power companies, ending up buying their own gas powered electricity plant). The cost savings in shutting down plant is pointless because of the time to restart, equally the same goes for idling - better to get a marginal profit than none at all.
When nukes come online things change, it is then not fuel cost but long term operating cost.
The problem is actually infrastructure - france does not have E7 storage heaters because of the additional charges for a high current supply, and in any case does not get as cold as say scotland oddly enough. We have substantial LV infrastructure capacity compared to say Italy or France, but other electric "ideas" like rechargeable cars could create problems. The per dwelling diversity calculation goes out the window.
Of course, one could write a book on it. As a basic rule of thumb it still holds true though. Fuel is always going to be cheaper than heavily industrially processed products of fuel.
No, because generating electricity and generating space heat are 2 very different processes. Space heating can be 98% efficient, electricity gen is less than half that.
that doesnt really add up.
As businesses, their margin is quite small. Even if it were zeroed, oil & gas heating would still be much cheaper than electricity at standard rate.
Yup. Plus supplying night power reduces day time peak demand, so less generation & distribution capacity needed, etc.
Boilerjuice quoted 63.5 online to me on the 6th. Other local suppliers were not quoting only giving a guide price that varied from
54 to 60p/l.
I have yet to ever purchase from Boilerjuice as they are consistently more expensive than our local supplier, 10p more expensive when I last bought in June...
Interesting telegraph article, take a peek at the graph on:
formatting link
it back to 12 months... odd that the sharp rise occurs the moment the bad weather starts at the end of November (not). Petol and disel have gone up but only more or less in line with the rise in crude prices. If those fuels had gone up like 28sec oil has in the last three weeks we should be paying around =A31.40/l for them.
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