JamesPa

Not yet, up until recently I've been charging largely on excess solar (I got the EV in May). A bit of playing with numbers suggests that a tarrif which has a few hours of cheap electricity (where I can charge my EV, do my washing/washing up and continue to run my hp, possibly with a bit of set forward) in return for a small penalty the rest of the time saves perhaps £300. A 5kW battery in addition saves perhaps another £200-300, which if the battery costs 5k doesn't make a financial case. Economy 7 (or something very like it) with no battery is looking like the winner based on a rough and ready analysis. I am left wondering what the circumstances are where 'professionally' installed batteries pay. Possibly if they are installed at the same time as solar panels? I am hoping I'm wrong!

Yes I do have both

That helps a lot because it gives me the idea to simplify the problem drastically by considering a two price tariff initially! Thank you

I have 4kWp of solar panels from 2011 on which I get FIT and export payments. Until recently I was self consuming about 50% of the annual production of 4MWh. I have a solar diverter already. I have not, up until now, been able to make the numbers for adding a battery stack up so I haven't got one (I cant see that they are justified environmentally over simply exporting to the grid). However I have recently acquired an electric car and, having finally defeated my planning authority over planning permission, will shortly be getting a heat pump, so the situation is about to change radically. Because of the wide range of options on what one might do with the battery, particularly if I opt eg for an agile tarriff, its a bit challenging however to work out how to crunch the numbers. Has anybody got a methodology for assessing the case that I could steal? I have all my half hourly electricity and gas readings so can project the demand profile fairly well allowing for the gas boiler->heat pump conversion.

I have not up until now been able to make the business case for a battery work out, so don't have one. Now I have finally defeated my planning authority and have planning permission for a heat pump, I will have to run the numbers again! Has anyone developed a methodology for assessing a battery eg with an agile tarif & heat pump that I could steal from?

OK so you agree that heat pumps are the solution, you just want them to be quieter. So it now becomes a matter of where to draw the line and, for some reason, you believe that the powers that be have, in this country (and others in for example the EU where, very broadly speaking, the requirements are similar), drawn it in the wrong place. The obvious response to this is: The current line is basically drawn at the level set by BS8233, which is, prima facie, logical and consistent. Where, in your view, should the line be drawn and why should an exception (which would further restrict their use) to the principles of BS8233 be made for heat pumps? Why is it more important to make this exception than to do something to mitigate climate change within current legal and building frameworks? In relation to your comment 'I chose to insulate and seal my property properly instead to reduce the need for heating. ' that is indeed laudable but, other than in exceptional circumstances, has nothing like the impact (on climate emissions) of a heat pump so cannot, on its own, be considered adequate progress towards a sustainable future.

I am assuming Octopus Cosy's 3 rates and 7 time periods are a reasonable proxy for saving the planet. It's complicated enough optimising the schedules to suit that but at least it's deterministic and also integrates with the battery setup. Probably so, but Octopus Cosy is really a battery tarrif not a heat pump tarrif. If you don't have a battery then I can't see it's useful to those with a heat pump.

True, but nothing in the ts & cs allows them to control your pump. Of course they could change the ts & C's so I'm guessing this is a first step to get people interested, with control to follow. TBH I wouldn't mind if they did control the pump provided that they do so in a way that constrains temp variations reasonably well and there is a fall back override. It's the way forward for grid balancing at reasonable infrastructure cost and means I don't have to buy a homely.

Ovo definitely have such a tarrif. https://www.ovoenergy.com/heat-pump-plus 15p/kWh up to a max of 6MWh/year. It looks like you can 'add it on' to other tariffs. Seems too good to be true as I cant find anywhere in the Ts&Cs a right to switch your heat pump off when they need to for grid balancing.

Actually the PD limits are 37dB(A) , 42 dB(A) arises because a notional background of 40dB(A) is added to get a BS8233 compatible calculation. If I install a heat pump I remove a gas boiler, so Im adding and subtracting at the same time, not just adding. The birds are noisier than this, as is traffic noise in most places. Mowers make a horrid noise and are intermittent which is worse. Your next door neighbours talking, and certainly their children playing, are way noisier (unless you are so far from them that the heat pump noise is irrelevant). You say you want to 'save the planet', so what is your solution to domestic heating if heat pumps are so objectionable?

You can to a limited extent (for both reasons), which is one argument for increasing the PD volume limit. However there is a practical limit to how big a box people can accommodate so it can only go so far.

Easy to say, but not available as an accepted manufactured solution (and not always practical). What is available and accepted is an acoustic enclosure costing 4K. Installations under PD (and doubtless most where there is express planning consent) are designed to meet MCS-020, which is derived from the 'desirable' levels specified in BS 8233. Why is that not good enough - why has BS8233 acceptable for everything else but not for heat pumps? Because they are 'new' whereas other equally or more invasive noise is 'old'? Fear of/prejudice against novelty which is in essence fear of change blocking the mitigation of climate change which, it seems, is not denied as a problem.

Im not including anyone specific, but there clearly are such people. However I do fear that your statement that heat pumps should not be deployed in their current state and that you don't want to hear others save the planet indicates that you may be in the delay, possibly until its too late, category. Adding noise attenuation to our existing housing stock before we deploy heat pumps, as you appear to suggest, isn't realistic. Many argue that heat pumps are already rather expensive and that is certainly true, so we also have to be careful not to add unnecessary cost otherwise its another backdoor way to delay. Furthermore there are many circumstances where heat pumps installed now do not make any more noise than any of the other disturbances we accept so there is no logical reason not to accept these. Existing nuisance laws protect us all from neighbours that are unreasonably noisy. The unfortunate fact of life is that we live in a crowded world that is going to get catastrophically more crowded if we don't fix climate change. We left it too late to do it without accepting some inconvenience, so inconvenience we must accept.

At present a COP of 1 gives no carbon advantage. Obviously this will change as the grid decarbonises. As to the central issue, objections to heat pumps, people will use almost any excuse to delay doing what they need (but don't want) to do. In fact its pretty classic, first deny the problem, then, when the evidence is incontrovertible, accept it but claim that current solutions aren't adequate and/or propose interim non-solutions and/or say we cant afford it, then say its too late anyway. That what big oil is doing and has been doing since the 1970s. Had we started doing something about it then it would be a lot less painful. Now there is no pain free way left open to us. It would be more honest if those who don't want to do anything about it for selfish reasons just say so. But of course then they would leave themselves open to criticism!

Just like gas and oil boilers, or like cars, lawnmowers, planes, people, ASHPs make a noise and, just like those things, they always will because they have to move air. In the vast majority of cases the noise is no more than (and frequently a lot less than, any of these things we are all very much used to and accept. So maybe you don't fear change, but you have displayed a prejudice against novelty and suggested that the roll out should be blocked as a result - which amounts to the same.

Typical fear of change is at work here. Same with electric cars. People see all the possible downsides of something new and none of the upsides. Worse still almost nobody I encounter seems to recognise that changing to ASHP is one of the critical things we must more or less all do to mitigate climate change. The ASHP/gas discussion is, in my experience, posed as one about todays running cost, not one about tomorrows societal cost and risk. To make things even worse, most people I speak to think that responsibility for mitigating climate change lies with the government not with individuals. Yet its individuals, not government, that have a climate footprint. Of course Government has a big part to play, but until we accept collectively that we are all responsible, not much will change or any change that does occur will be too slow. In reality we need to do four major things to reduce our individual climate footprint: 1. Heat our houses using an ASHP 2. Buy only stuff we need, not vast amounts of stuff we are convinced by industry that we want 3. Stop using planes other than in very exceptional cases. Use public transport predominantly and electric cars where that isnt practical 4. Stop eating meat and dairy (and produce that is flown in); or at worse cut consumption by 80-90% Actually the first is the easiest as it doesn't require a lifestyle change. 2-4 all require lifestyle changes.

... and how much it contributes to climate change. But apparently 'conservation' trumps everything. My LPA wouldn't let me fit double glazed metal framed windows in a refurbished property when single glazed metal framed windows had to be replaced. So we were forced to put in new single glazed metal frame windows. This was in a property originally built in 1860. Would it even have had metal windows when first built - I doubt it. Nuts.

That says it all.

Someone involved in the design must have had shares in Honeywell!

The problem with this is step 1, knowing your heat loss. Heat loss surveys are not always accurate and can be wildly inaccurate, so whilst they are a starting point it's unlikely this alone gives the optimum curve. If it aint broke don't fix it does of course apply but the lowest possible flow temperature will give you the highest efficiency (roughly 2-3% change in efficiency per degree, which can soon mount up.). @JohnMo suggests an iterative approach based on experiment, which is the only one I can see can possibly work, unless your heat pump features auto adaption or you have a third party ft optimiser such homely. Whether it's worthwhile depends on how much you want to chase efficiency.

@Nevik This is an area of some disagreement, here is my take and experience, you will need to decide for yourself. "Proper heat loss surveys" can be utter garbage if the surveyor (for example) ignores fabric upgrades they cant see (which some do as a matter of principle) or puts in an unrealistic value for air changes, or miscellaneous other sources of error. The spreadsheet/software looks sophisticated, but as ever GIGO applies. Personally I wouldn't rely on a 'proper heat loss survey' alone unless you validate both the inputs and the calculation and also have some independent handle on air change rate. I had two done, one of which I paid for, and they were total nonsense because the surveyors ignored invisible fabric upgrades ('if we cant see them how do we know they are there' was their argument, an argument which I have heard from others since) and double counted room to room losses. To be tolerably certain I would have a survey done, then check (a) the u-values used (b) how they have treated room to room losses (they should be counted for for radiator sizing but not for whole house sizing, unless room to room gains are also counted) and (c) what value for air changes has been used if you can collect smart meter data from a season where you operate your boiler fairly constantly and are heating your house a good proportion of the time, then do various plots eg daily consumption vs degree days, average power over 3, 6, 12, 24 hrs and utilise what this tells you Do the rule of thumb calculation, although a divisor of 2200 or even 2000 is also suggested by some and there are arguments for various values in between, probably depending on the assumptions you make about boiler efficiency and location. For the second and third of these, if you can, make some intelligent assumptions about your boiler. If its very old then it probably has an efficiency ~75%. If its a condensing boiler but you have plumes of vapour coming out of the flue (ie the norm in the UK), then its not actually condensing, so efficiency might be ~90%. If its a modern condensing boiler, run at a FT of 55 or less, and there are no plumes of vapour, then it is condensing and might be running at an efficiency of 110%. All figures rough and ready. If you cant work out what assumptions to make, at least you can account for the uncertainty. Once you have all of that (if you can be bothered to go to this much trouble) then see what this tells you. If they are all tolerably consistent then you are good to go. If there are major discrepancies then I would suggest you might try to work out the explanation. In my case the discrepancy was a factor of two, the difference between 8kW (measured) and 16kW (calculated), a difference which has major knock-on consequences. If your house is low loss (eg ~3kW) it matters less because you are anyway going to be limited by available models and the need to have sufficient capacity to heat DHW, so you are probably going to end up with 5-6kW anyway. All that said a tolerably oversized heat pump is probably not a disaster unless it pushes you into consequential actions such as upgrading pipework, requiring planning permission or something else, all of which are more likely for a high loss house than a low loss house. An oversized pump will cycle more than a right-sized pump, possibly even at very low temperature. This does reduce efficiency, but nobody really seems to know by how much with modern inverter driven pumps (perhaps a topic for another thread sometime). Heat loss surveys will tend to overestimate because that's 'safe' for the installer. Whether its 'safe' for the customer depends on the circumstances as exemplified above. It sounds like your house fits into the high loss category in which case a sizing error might make a massive difference to the scale of works needed.

I seem to remember reading, when skipping through the Ideal (R32) installation instructions recently, that it would not start unless the return temp was greater than 17C,m and they were recommending various ways to ensure that this was the case.. This would be consistent with the message and, if it means what it says, is a bit mad!

If all you want from your thermal store is long showers, then thats just a big domestic hot water tank, its nothing at all to do with buffer tanks.

The latter. Apologies.

I haven't seen any, but then I haven't done a comprehensive trawl. Fan radiators almost certainly don't follow this rule, and I imagine very tall rads may not. Its not going to vary materially from manufacturer to manufacturer, its just the physics of convection. Some rad manufacturers quote the formula in their literature, giving a value for the exponent. Every one I have seen the exponent is 1.3+/-0.02