Help! This piece is not for anyone's amusement, entertainment or erudition. I am trying to decide between two heating systems for our cold and unwelcoming cottage without having any definitive data to work with. Writing things down often helps to produce clarity of thought.
Here's the issue - we can't get oil up our drive, we don't want gas bottles and we haven't got storage for biomass. So it has to be electricity. In these days of environmentalism the air-source heat pump (ASHP) is thrust upon us by quasi-religious zealots, and loads of government money. It has to be good, doesn't it? On the other hand, there are companies out there offering modern ceramic-core electric radiators (ER) claiming to be far better. Cheaper to run, more responsive, easier to install. But how does one cut through the rhetoric to get to the facts? That's the hard bit. Admittedly there are many variables and on this basis no one is willing to put the neck on the block. Running costs are not the only consideration. And, for the record, all the supply and installation quotes have been in the same ballpark.
Installation – electric heaters are installed in one day – screwed to the wall and connected to the existing supply. The ASHP requires radiators, pipes, water cylinder, manifold (if under-floor) and generally having the house turned inside-out for a week – or for months given my experience of these Highland boys!
Guarantees – the ERs are guaranteed for 10 years, with a policy of replace not repair. No servicing or maintenance is required. On the other hand the ASHP is guaranteed for just three years, conditional on an annual service at about £300 a go. If the ASHP breaks down, we have no heating. If an ER fails, well that's only one.
Operation
If I was to finish this piece here, I think you would agree that ERs win every time. At this point I can see no reason to even consider the ASHP. But as yet, we haven't discussed running costs. It is all very well having a perfect system but if we cannot afford to use it then it's rather pointless. Now this is where it gets really difficult and murky; no one will give a straight answer to a simple question. I know that the variables are endless and sometimes unknowable – construction type and materials, glazing, insulation, location, weather, human behaviour! As a result few are willing to state figures. And given the very different ways these systems work it is so hard to compare. Both agree that the heating requirement of Heather Cottage is about 11 to 12kWs and that both systems use the same electricity at 14p ish per kWh. From the ERs we get 11kW of heat from 9.6kWs of input. The ASHP generates its 11kW from a draw of just 3.6kWs. Multiply kilowatts by the price and by the hours of operation and suddenly it looks like the ERs are going to cost three times more to run. But it is the time factor that is so hard to pin down. Using the earlier example of turning on, the ASHP will cost 3.6 x 14p x (say) 2 hours or £1.01. The ERs will cost 9.6 x 14p x (10/60) or 22.4p. So it is that time factor that is so important. But for how long will each system need to be drawing power? That's the unknown! We know that the ASHP, once on, needs to be left all the time. It is too unresponsive to operate it otherwise. It constantly switches itself on and off, but for how long, in any typical 24 hour period is it 'ON'? Half the time, twelve hours? 3.6 x 14p x 12 hours is £4.75 a day or £1700 per year. I also know that if I leave all the ERs on full blast for 12 hours it'll be like a sauna in here. A figure that I have extracted from the manufacturers is that if I leave five of our proposed ERs on at twenty degrees that will cost £191 per quarter and that if I use them for just three quarters of the year it will cost £573 per year. Work that backwards and they are suggesting that 2.5 hours a day will be sufficient. Is that realistic? I have no way of knowing. This does not include the hot water whereas the ASHP gives you warm water all the time. Neither though do I want my bedroom to be 20 degrees. That's far too hot. Sixteen degrees, maybe? All those variables... There is a curveball to deal with. The Government is throwing money at ASHPs. There is an interest-free loan of £10,000 available. The ASHP quotes are higher but they attract VAT at just 5% which makes the ERs seem more expensive. There are also the Renewable Heat Incentive payments to consider. The quote suggests that this could equate to £300 per quarter. This value is based on the installation, not the amount of electricity consumed. Bizarrely, I could have the ASHP installed, not use it, and receive an income of 7% for seven years on the outlay! If I do use it (which is the entire purpose of this project) these payments will off-set the projected running costs quite considerably. Nevertheless, I believe that the RHI payments should be treated as a bonus. It is an artificial device that does not contribute to the underlying calculations and decision-making process. It is a political tool that could be withdrawn and cancelled at any moment. If our dozy leaders decide that supporting the national economy takes precedent over the global environment then it'll be gone in a moment.
So, decision time. Electric radiators (easy to install, easy to operate, no maintenance, but might be expensive to run) v the ASHP (installation nightmare, intrusive, noisy, few guarantees, might be dearer to run , even than the ERs, but with lots of Government support)?
In writing this I have thought of a number of illustrations and analogies. The aforementioned supertanker is a very efficient means of transporting huge amounts of oil. But if there is no need for such vast quantities, then it becomes the wrong solution. My mother goes to Thame market and buys peaches by the tray-load. Twenty-four peaches for a pound is extremely good value (or whatever the deal is) but if she has no use for 24 peaches then all at home are urged to gorge on slowly rotting fruit before they have to be disposed of. They might be cheap, but that is not good economics. Four peaches for 50p is better value if four peaches is all that is required. I have been looking a photo-voltaic cells. They produce 'free' electricity whenever the sun shines. The time when the sun is shining is the time that electricity is least required. I pointed this out and the consultant struck back with the advice that we could at these times do all our washing, ironing, DIY, battery charging... But when the sun is shining I want to be out enjoying it not being at home using up energy for the sake of it. It is on that cold and dark winter's evening that I want free energy – exactly when it is not available. Here is the point of economics: if my pre-installation requirement for electricity is, say, 4kW per day and my array is giving me 10kW, my saving is still only 4kW. The fact that I have another 6kW to use or lose, or sell back to the grid for a third of my buy price, is beside the point. I might be able to use it but in reality it is surplus to requirements. I think the ASHP falls into the same category. Very efficient, but has to be left on all the time, producing heat and warm water whether that is required or not. They have sophisticated control mechanisms to mitigate this but I still feel that it falls into the supertanker/peaches category!
I think I have made a decision. It will cause ructions. Yes, ructions in the family. My father and brother are both ASHP enthusiasts. I will be ridiculed and derided. They both have new-build houses that are super-insulated and that are located in the south of England. I live in a shack in the Highlands of Scotland and there are plenty of tales here of ASHP installations that have subsequently been removed because they don't work at these latitudes, or that they have to work so hard that they become completely uneconomical to run.
Comments of a practical and constructive nature are welcome. Please point out the gaping holes in my reasoning. Feel free to share this with anyone who can add meaningfully to the debate.
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