How does boiler efficiency work in real terms? I have a couple of 80% efficient oil boilers and I see that I could buy a 95% efficient boiler. Does that mean the new boiler would use ~20% (0.95/0.8 = 1.19) less fuel? Or are things more complex than that?
You also have to factor in the strong tendency of the modern condensing ones to go wrong in expensive ways that service engineers find hard to fix. Your choice being to pay through the nose for a new control board or the time he spends scratching his head trying to isolate the fault.
OTOH Perhaps the folk I know with them are just unlucky...
My boiler isn't particularly efficient and in an insane location (the loft) but it works reliably and I am in no hurry to replace it.
In theory yes. But manufacturers tend to quote peak efficiency - water coming in cold, boiler running at full load. In real life this situation is far from the norm, so SAP energy ratings use a SEDBUK efficiency, generally (unless its changed since I was involved in this stuff) taken as
50% full load and 50% at 30% load. Check outGenerally changing a boiler for the sake of changing is not going to be cost effective and an oversized boiler may well deliver sub par efficiency regardless of the stats.
This was my thinking when someone suggested we get things repaired, rather than always going out and buying new. Much equipment has become so complex that you then have to rely on the individual manufacturer, who can charge stupid prices for the parts. Simplicity has it's benefits, of reliability, simple maintenance, cheap pattern parts and a local guy prepared to mend things and thus longevity. Perhaps it could be the greenest measure of all, cutting down on material, manufacturing, replacement and disposal costs but of course it doesn't suit manufacturers. I'd like to see an honest comparison though.
If you use the SEDBUK figures which are adjusted to reflect more real world like conditions than the "perfect" scenario results that the makers might like to claim, you get a closer answer. When looking at manufacturers figures you also have to take note of if they are comparing gross or net efficiencies.
However in simple terms moving from say a 70% to a 90% efficient boiler does suggest that for every £1 spent on gas you would be wasting 10p rather than 30p. Obviously against that you have to factor the cost of a change, and the projected lifetime of the replacement. For most cases its not usually (yet) cost effective on fuel use savings alone. However if your usage is very high the sums may indicate different.
One of the reasons I rejected combis when I went "condensing". (I already had a "hot tank" for a shower but had to change it for one with a coil, and plumb it into the existing DHW).
Ta. I'll look up my boilers and go from there.
We're only fairly recently moved in, but my estimate is that we'll spend around £2500 on oil over the course of a year, so £500 saved every year is interesting if it's real.
Jon
Yup with those figures it gets more interesting. The efficiency gain on oil burners is somewhat less than for gas ones IIUC, and also the modulation range is typically smaller - which means less gain at part load and more negative impact from over sizing.
In my case I was counting on saving around 200 - 300 / year which will pay for the boiler in three years (if I don't cost the time I spent installing it)
But for the average punter, a servicing contract will wipe most of that out. With my Band (D?) lump it came "free" with the house, and in 24 years has cost me a fiver for a new thermocouple and a wodge of fireclay, plus a couple of hours spent hoovering cobwebs and bits of straw out of the burner.
This is uk.d-i-y you know :P
You must use the SEBUK figures rather than any manufacturers claim. (As others have stated.)
£2500 is still quite a bit to spend on oil. I find it best to always ring a number of suppliers before making a purchase.My oil consumption did drop when I installed a new boiler a few years ago. I have a theory that it has paid for itself, as it was a D-I-Y installation. I installed a non condensing boiler just before they were disallowed.
Yes, my point being that I'll quite happily look after a stone-age boiler myself, but wouldn't be confident to do the same with a modern one ...
It's an estimate, but since I started measuring weekly this winter, we've been getting through around 100 litres a week. It's not been overly cold yet, so it'll get worse and of course in summer there will be far less oil used.
Jon
There is no law requiring you to take out a service contract. Buy a decent boiler in the first place and just pay for any repairs as needed.
That's my approach too despite my tongue-in-cheek dig at this being uk.d-i-y.
Why? It's a bit like saying 'I was happy fiddling with points and carbs on an old car but not on a new one. That's because new cars have dispensed with those stone age things and use systems which don't need constant fettling. But you still have fuel going in and being burnt...
You actually have independent suppliers still ?
All ours bar one tiny outfit have been bought up by the Certas monopoly. They still trade as if independent entities but you can order from A and get a delivery by B (supposedly rival companies).
It annoys me that we cannot get dual fuel tariffs with no gas. Despite the fact we are in the danger zone for a buried high pressure pipline!
You might also consider ground source heat pump and get the government subsidy. Installation and running. (Renewable Heat incentive) The thing can be connected to your existing heating system in most cases
Do you work for one of the con merchants selling them to retired elderly couples who stand no chance of understanding the tradeoffs?
It can but it won't work properly since an ordinary CH radiator system requires much hotter water than a ground source heat pump can provide.
The only purpose for installing ground source heat pumps is in a new build where the building can be designed around the intended heat source and even then the electricity usage and maintenance is a nightmare. I helped someone with a bad installation once and saw first hand what the cowboy installers had done. They would have been better off on oil CH once compressor repairs and callouts were included.
I'd be interested to see an example of GS CH that actually does work.
Then, I suspect that your total annual usage will cost less than £2500.
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