Hi @ =adamm, I am 70 miles south o' the border, in North East England. But converted oil boiler to ASHP a year ago. No regrets, but quite a learning experience on the way.

Our 1992 house was EPC D (58) before, and is now EPC C (76 after). We had a Worcester Danesmor 26kW system oil boiler with thermal store. Oil boiler over 20 years old, cost nothing to maintain and uber reliable. It was getting on and would have needed replacing and I didn't want to continue burning oil.

We used to get through about 1500 litres oil a year, or 15,500kWh. Boiler efficiency would be 80% at best, so about 12,400kWh for CH and HW. We have a long burner which we have on most nights in the winter season, less so now we have ASHP. It would burn about 2,500kWh over the winter at 60-70% efficiency. We used oil filled rads as well in a few rooms for heating to avoid putting the central heating on. All-in including electric for heating & cooking as well, around 20,000kWh/annum, for a 150m2 property or 133kWh/m2/annum. We were spending around £2.5K a year on oil, firewood and electricity combined.

We went with Solar PV+battery+ASHP so our consumption is skewed a little by micro-generation. Year-end figures are looking like 7,000kWh total. 4,000kWh electric import, self-generated solar PV 4,000kW of which 1,000kW exported & 3,000kWh consumed, so solar PV has contributed 43% of our requirements. Cost of electricity & fuel will be about £1,25K, so we've halved our energy bills. That's largely due solar PV plus time of use Cosy Octopus tariff & importing lower rate electricity, storing in the batteries and using it to power our daily needs.

We don't run our ASHP 24/7 contrary to perceived wisdom and best practice. We run for about 17hrs a day in the heating season. We prefer it cooler overnight, so it goes off at 9pm and on again at 4am. The preheat warm up time in the morning is long and slow, and it is quite energy hungry until the system volume is up to target flow temperature. We have a small-ish 10kW ASHP Grant Aerona unit, but it does the job. If the weather is particularly cold we can light the stove to provide an extra 4kW or so.

So in summary, with the ASHP+Solar+Batt:

House imported energy consumption now 20%. Was 20,000kWh/annum, now 4,000kWh or 7,000kWh 35% without our solar contribution

Annual energy bills halved, was £2.5K, now £1.25K. The majority of this is due to Solar PV and TOU electricity tariff however.

Annual CO2 emissions slashed to 20%. Was Oil: 1500 litres x 2.52kg/litre = 3.8tonnes. Electricity 4500 kWh x 0.233 = 1tonne. Say 4.9 tonnes. Now: 4000kWh x 0.233 = 0.9 tonnes. (I'm dubiously considering burning fire wood as 'carbon neutral', which is very debatable considering transportation, drying, etc!)

Next post will give my views on ASHP MCS SCOP estimated vs my guesstimated actual...

@adamm. MCS energy consumption predictions for my Grant 10kW ASHP were well out for both estimated existing and future. So far out as to be disregarded as unreliable. MCS estimates are based on EPC info, which is not a reliable source, so treat any MCS estimates with a large pinch of salt. If you're on oil and electricity, you know exactly what your annual energy consumption is now. 🙂

MCS SCOP performance estimate for heating was 4.11, based on max LWT of 50degC. That's optimistic. It has probably averaged 3.0-3.5 SCOP based on my monitoring but I now have a max LWT of 45degC. At that condition MCS/Grant claim a SCOP of 4.49. It's nowhere near that.

MCS and most OEM SCOP data does not include for defrosting in winter, or system inefficiencies, some of which are near unavoidable for a retrofit, so I would knock 25% off any SCOP figures quoted at you for a typical retrofit. Some clever installers can get much better SCOPs, largely due to better system design and commissioning parameter setting. Typically however, you'll not get what the manufacturer's claim.

MCS SCOP performance estimate for hot water was 1.75. That's low, I think it's between 2.25 & 2.5 as I heat to 55degC tank temperature. Hot water generation with ASHP is quick and efficient.

I've been manually monitoring flow and return temperatures, flow rates and power consumption during heating and hot water to try and ascertain system SCOPs. It's not scientific, but has shown that the MCS predicted SCOP for heating will never be realised. This is due to system inefficiencies - the stuff Grant chucked at the install that reduces efficiency such as low loss header/volumiser, secondary pumps, pre-plumbed cylinders with motorised 2-port valves.

But, perhaps more significantly, Grant's SCOPs for their 6,10,13,17kW ASHP products at reference design condition A7W35 and A7W55 are, on average, 20% higher than the product manufacturer Chofu's data at the same condition. It's the exact same product, just badged up as Grant. Make of that what you will, but Grant are not the only manufacturer with what appear to be exaggerated published SCOPs, I have heard a rumour that Midea are under the spotlight at the moment...

Any regrets - none. I absolutely love being off oil, the energy savings come from the ASHP, but the energy bill savings come from the Solar PV & batteries.

@allyfish Thank you very much for all the details you provided, very informative and helpful. 

Re EPC & heat loss calculation, that's my worry as it is a model as good as the data used... without verifying it using running ASHP its difficult to be certain how accurate it is. But sounds like your case is definitely a success story.

Please can you advise What windows and insulation do you have? Have you done any insulation improvement or draft proofing? Please advise.

Hi @AdamM

We have had a Vaillant 6.7kw ASHP fitted to a 180m2 house in the North East of Scotland for the last 19 months.  Wouldn’t swap it for the world!  This year we added Solar PV / Battery and an EV into the mix for go measure.  

Our house is 20 years old next June.  We have done zero insulation wise, just added the heat pump in place of an OG boiler.  We would have been round 2500 litres of oil a year ( we didn’t get a full year in the house before removing the boiler).  We have made all the setup changes as recommended by the great folks on this forum, and we as a family love it.  Take the info with as much of a pinch of salt as you need. It’s the only measuring equipment we have so it’s all we refer to these days.  Like I say we are happy, very happy. No smelly utility room, no worrying about oil costs, no worrying about running out of oil, no electricity/fuel bill since solar fitted 11 June this year(there will be one this month).

good luck on your journey.

Drew

Posted by: @adamm

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Please can you advise What windows and insulation do you have? Have you done any insulation improvement or draft proofing? Please advise.

Hi @adamm, nothing special, 30mm sealed argon filled PVCu DG units, to front of house 2yrs old, to rear of house 15yrs old, 200mm loft insulation. PVCu doors.

The biggest change in EPC rating was LED lighting throughout so the surveyor said, never mind Solar PV & ASHP! The SAP assessment method for EPCs has a lot of flaws. ASHP is classed as electric heating so has never scored highly, and used to make some EPC ratings worse over oil or gas, that’s madness! The latest version of SAP has addressed that I think. Not before time! 

Hi @adamm and welcome. Just to add my experience....

We live in the Cairngorms, approx 170m2 old 4 bed detached with solid stone walls, suspended timber flooring and (until improved) single glazed sash windows. When we bought it (Oct 21) the EPC said E (43) but now after various improvements the last one we had done (Nov 22) was C (79).

We replaced the oil boiler with ASHPs after a few months, so don't really have a comparison. We have 2 x 12kW Samsung units to cope with demand in what was (and remains to a much lesser extent) an old and leaky property. I've never seen any heat calcs, despite asking, and suspect these exist on the back of an envelope. I can give you some real world experience though.

Since the ASHP went in we have installed secondary glazing (Invisitherm from Glaze & Save), which is pretty good and really made a noticeable difference in each room. We've also used 4mm thick thermal lining paper (Wallrock) on exposed walls. Again this makes a difference, if only taking the edge off things. I hired a thermal camera and then went round sealing every gap I could get access to with decorator's caulk, even fitting some toddler-proof caps to sockets to stop drafts through them. We've also installed 5.5kW of PV and 10kWh worth of batteries. These have been in for 12 months now and our stats are included below. 

Experience has been mixed and a huge learning experience but I'm glad to be off the oil and have created a more efficient house. 

1. Both our ASHPs failed last winter, within a couple of weeks of each other, due to "refrigerant leaks". These were promptly replaced under warranty but the deterioration in performance may have been contributing to some eye-watering power consumption beforehand. On some really cold days we were pulling way over 100kWh/day. Once sorted the consumption dropped to 80-ish. Still high but thankfully not too many days like this and you need to look at the year-round picture. 

2. The system coped with extreme temperatures although is power hungry. Through operation (and with help from people on here) I learned how the house responds and how to operate the system better. Given the house takes ages to get warm, I find it best to operate 'low and slow' pretty much continuously over the winter months. Experience has taught me how to adjust weather comp etc and I've been pleasantly surprised how efficient the system can be if left on slowly.

3. For a bit of context, our 12 month headlines (Sep 22-23) are:

• Total house consumption 13,277kWh
• Grid Imports 10,826kWh, so PV contributed 20% of our annual needs.
• PV generation 4,192kWh, of which we have utilised 63%, the remainder being exported.

We're not on any special TOU tariff so that's the next step for us to try and lower bills.

So, would I do it again? Yes, but knowing what I do now I'd be much more inquisitive and challenging on the heat calcs and the whole set-up/commissioning process. Given the improvements we've made to the house I dare say that using 2 x 12kW ASHPs, with all the attendant pumps, buffer tank etc, isn't the most efficient way to go and a simple 1 x 16kW pump (say) would do the job. Given the time again I'd also explore a hybrid system with infra red heating for the upstairs bedrooms. 

Anyway, just another experience to help your deliberations. 

Simon

For another cold climate user, I am a little to the south and east of @Dunlorn but quite elevated and exposed to the east. Self build 180m2 timber framed bungalow in 1992 with suspended timber floor so in accordance with the regs of the time, a house with a howling gale blowing through. 14Kw Ecodan installed in 2019 to replace LPG and log burner as heating. All the microbore and existing rads were removed and replaced with 15mm feeds to K2 and some K3 rads.  Solar thermal and PV hybrid panels installed at the same time.

No idea what the EPC before the installation would have been but EPC C afterwards.  When building I fitted storm grade Nordic pine DG windows and top quality doors. After fitting the HP system the loft (wind tunnel) was filled to about waist height with insulation.  Very full heat survey done with the installer who was very experienced with HPs. 

Total energy use since HP fitted is around 11000 Kwh/annum with about 6600Kwhs going on heating. We too use the low and slow heating system with the flow temps always around 35C on Mitsubishi auto adapt setting.  We do set back at night to around 15C and the recovery time in the morning is short, about an hour. The house is maintained at around 19 to 21C all winter and in the coldest months is pulling around 45Kwhs per day. Like @Dunlorn we keep out the drafts but have to accept a high windwash in the structure that cools the house.

Very impressed overall but as others have mentioned here the installer is the key. He knew my requirements and his advice and installation was spot on. He was so confident that he paid for an independent Nappit survey to ensure the job was done right.  I use the Mitsubishi's service package and the local (Perth) agents are absolutely top of the game. They spent a morning fine tuning the system to ensure maximum efficiency on their first visit.  I am a happy, and warm, customer! 

@drew-pa 
Hi,

Thank you for feedback and information, i've read your yearly review, very useful.

@dunlorn 
Hi Simon, many thanks for sharing your journey experience. 
I assume that apart from Wallrock, your walls have no other insulation.

Thank you

@dunlorn 
Hi Simon, many thanks for sharing your journey experience. 
I assume that apart from Wallrock, your walls have no other insulation.

Thank you

@adamm that's correct. The EPC had a recommendation for internal/external wall insulation but with all the disruption I decided against it. Just have really thick solid stone so the place takes ages to heat but does benefit from a bit of solar gain. The most challenging days are dull and windy - no solar gain in the mix and a gale blowing through the suspended floor void. 😊