Posted by: @bontwoody

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Off piste I know but i cant resist a probability calculation!

Not at all! The real world is much more complicated, none or two or more patients might have died (it's a small sample; maybe all the relevant risk factors weren't included in 'the model' that came up with the 10% probability; whatever), I just kept things simple to, I hope, make the point that probabilities are usually but not always useful at group and population levels, but their usefulness for individuals is far less than is usually supposed, what I called the collapse of the probability function. Another similar example: I might know that I will get solar gain on average for 60 days in a year (60/365 days = 16% probability), but what I don't know, despite it being the practical thing I need to know to decide what to do now, is whether I will definitely get solar gain today until it does, or doesn't happen today. Perhaps instead of solar gain we should call it Schrödinger gain.

@cathoderay I don’t think I can add a lot to all that has been said though that won’t stop me from trying!

Regarding installers; I would endorse the Octopus approach, though they could not encompass my requirements when it came down to it as I required a rather non-standard approach as I wanted to avoid a huge DHW tank due to lack of space and thus wanted a Sunamp system as well as wanting the heat pump mounting several metres off the ground on a wall, I did have some very informative discussions with their plumber and electrician who carried out a survey for me. It was obvious to me that they were prepared to go to great lengths to try and fit as many systems that would be very good installation all-round. They do have what they referred to as the ‘scope’ and they explained that this was was within narrow but very likely to work well parameters; they are anything but ‘Grant Harvesters’. As mentioned, mine didn’t fit within their scope but they will certainly do good work for anyone they do survey and agree to install for.

I researched my own requirements for over a year and tried 20 + installers - many of whom were obviously box ticking the components they were prepared to fit and of course ‘They knew Best’ Many companies were not prepared to install in my area and yet others reckoned to provide a certificated install without even being members of MCS or the other organisation recognised for this work. Most companies did not wish to even carry out heat loss calculations so shortlisting left me with no more than 3 companies to consider in the end. Only one would listen to my wants and desires and with a few tweaks they suggested, we had a working ASHP install!

Just one other comment: Running 24/7 or switching off for so many hours and the relative costs of doing so, one ‘cost’ that hasn’t been given a great deal of attention or value is that of ‘Comfort’ Though we have only had a working system since February 2022, I can say that we feel the 24/7 approach has provided us with a very even temperature without any cold zones at all, in addition there are no hot zones either. The air and fabric of the building is so evenly heated that wherever we are in the house, we are not aware of radiators/emitters at all - just even warmth! We are set up with weather compensation and LWT - all thermostatic radiator valves are presently fully open pending any further tweaking if required. Regards, Toodles.

We installed our heat pump in January and we are definitely saving money now that it is combined with battery and solar. Octopus Tracker Tarriff certainly helps but so far in summer we use virtually zero grid energy to power our hot water and there is no heating requirement. Any background grid use is cancelled out by what export back to the grid. We are now in September and this month we are in profit.

we got the equipment in a mixture of grants and loans, but we are still better off than when we had no renewables and relying on oil. 

winter will be interesting but I suspect it will still be cheaper than it was last year and when you factor in the summer months I have no regrets whatsoever.

Also, replacing oil with ASHP and bringing in solar and storage has another tangible benefit in terms of your EPC. My house has gone from a C rating for environmental friendliness to an A rating and from a D to a B for energy efficiency. 

this is worth thousands on the value of your property, as is the infrastructure itself.

And one other point I should make. Ours was installed in -10. It performed, immediately. It was turned on at 6pm and from a cold start in -10 temperatures and dropping we had heat and hot water that evening. 

we have underfloor downstairs and it took until the following morning to hit our normal temperatures but the upstairs radiators had the upstairs up to temp in a matter of hours. 

ours was the Grant Aerona 13KW, installed by a firm who are gold level Grant installers.

@marvinator80 Hi, thank you for your comments - it sounds like you were in a similar position (oil) to ours, so it's good to hear you endorse the HP and have no regrets. We think we're probably going to ignore the "one-size-fits-all" deal and design a system that will better fit our house and lifestyle (although when I say design, I mean get in a HeatGeek designer!) to be sure we're getting the best fit. I hadn't thought about it adding value to the property, so that's another plus, too. I asked a local estate agent, but he was surprisingly non-committal - he basically said for it to be an asset, we'd have to prove that it has saved us money over several years.

Did you have a new hot water tank for your HP? As ours is a Combi boiler, we don't currently have a tank at all, but I've read HP tanks are bigger and we'll need to work out where we can put it. Was that a problem for you? And also, do you have as much hot water as with your oil boiler? It probably sounds daft, but this is important for us, as we have animals/livestock, and coming in during the winter cold and wet through is not a good time to have insufficient hot water!

Thanks

@cookie197 hi Cookie. 

yes, we had a 250l tank installed. We put it where our combo boiler used to be. It’s bigger than the boiler was and it’s a bit unsightly, like a Dalek out of Dr Who but we got round that by boxing it in. Now it’s a good extra cupboard for drying things. The tank itself is insulated so doesn’t radiate heat but the pipe work does. I’ll put some pics below. 

I researched and chose our set up myself and made sure the installers were MCS registered. Then I just submitted the paperwork through the Scottish Government Scheme (Home Energy Scotland). 

I told them what type of ASHP, what cyclinder, the panels, the battery and the suppliers and all was fine. 

in total I got £26,500 of funding. £11,500 as grants and the rest as a ten year interest free loan. So I pay about £124 per month for that. 

Energy Performance Certificates definitely add value to the property and I think your estate agent is being a bit clueless as to the additional infrastructure value. 

Would I have changed to ASHP alone without solar and battery? Probably, but with less enthusiasm. With the solar and battery so far for me it’s been a no brainer.

Here’s my full home set up. I have have an Eddi hot water diverter which means that the solar will heat the hot water to extra hot before it starts to kick anything to the grid. That has been surprisingly good.

I also sold my boiler and oil tank on Gumtree for a grand. That was great, guys just came and took it all away on day one of the ASHP install once the boiler had been taken out.

@cookie197 For your information you can get slimline versions of HP tanks. I am looking at one at present as it needs to fit in the space currently occupied by my solar tank which is 550mm in diameter. As an example: https://www.gledhill.net/products/unvented-cylinders/stainlesslite-slimline/

As mentioned our HP is a high temperature version and will produce DHW up to 55C on its own. The test for me was the Wife and her bath temperature ( 45C ) and I am still alive to tell the tale! So big green tick. I would not worry as the new HPs are quite capable of hot water production and can be programmed to simply maintain the hot water temperature by heating up only the amount you use (indirect version of a combi). I believe the insulation of new tanks is very low in losses, another reason I am upgrading in October as mine shows a distinct heat drop after a couple of hours due to its design.

@technogeek If size of DHW tank is still a problem as it was for us, too tall when slim, too fat when shorter, I would suggest considering the Sunamp Thermino range. We have the solar PV powered or grid model (ePV) and the MCS preferred size meant we went for the 210 l capacity. Very neat with just a cold feed in and a hot feed out plus electrical connections; we are very pleased with this design however there are other versions including ones for HT heat pumps. Regards, Toodles.

Grant also do an “integrated” cylinder now. I would have got that, in retrospect.

https://www.grantuk.com/products/cylinders/quick-recovery-integrated-cylinder/

Posted by: @marvinator80

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It was turned on at 6pm and from a cold start in -10 temperatures and dropping we had heat and hot water that evening. 

You must have very long evenings! Or the house was already at near design temps despite it being -10 outside, or it is a very low heat loss house with a very low thermal mass, or you had heat, but the house wasn't that warm. Most heat pumps are not going to achieve anything like this sort of near instantaneous heating, especially given that most are set up to heat either house or hot water at any one time, not both at the same time, and I am not sure if I may politely say so that it is that helpful to suggest they can, without elaborating on how to achieve such rapid heating.

Likewise the Grant integrated cylinder look to me like a pretty standard pre-plumbed/wired cylinder, which installers like because it makes the installation easier. However, the thing that worries me about the Grant integrated cylinder is the coil surface area, which is 2.3 sq metres (buried on page 6 here). My understanding is that large ASHP heated cylinders typically need at least 3 sq metres of coil area (lower LWT compared to boiler means bigger coils just as it means bigger rads etc).

I think you will also find your current cylinder does lose heat, even Grant admit their integrated ones do (they give the data in kWh/24h which of course will mean nothing to most people, who will want to know how long before my hot water gets cold when not in use). I can tell you that my 200L Telford Tempest Heat Pump cylinder (which incidentally has a 3.3 sq metre coil, and a reheat time from cool of around 30 mins) loses about 5 degrees/24 hours in summer when the hot water is not in use. Of course, the rate depends on the DHW temp and the ambient indoor temp, but that is a rough guide based on my experience (and data - the DHW tank temperature is one of the variables I collect).