@bami My feeling is that the picture shows an expansion tank not a buffer, so that is good. I take it you were not given the specs and system diagram before it was installed? I thought that was mandatory?

A 120 square meter bungalow with decent insulation should be around 5kW heat loss. Im on my second one now and both had 5kW heat pumps with no problem. I would say my current bungalow has worse insulation than yours and is a lot older with several external solid walls.

I think if you can obtain the specs and they indicate a lower size then you have an improved position when asking for a replacement. Perhaps @editor you can advise?

I understand your financial position but you will soon burn through more electricity than a reasonable monitoring system will cost if your system is set up badly. You dont need to go the whole hog and get a heat meter, thermometer probes would be good enough to get a good idea. I use openenergymonitor and can wholly recommend it. This would be fine.

As I mentioned though an alternative course would be to get Homely which might be a similar price or cheaper, there are people on here who use and recommend it and you wouldnt need to understand the theory of heat pumps as it does all the optimising for you. If your SCOP is not better before next winter I would certainly consider taking out a loan to pay for it and use the savings to pay it back.

You should be able to approach the oil usage figures with the heat pump (COP adjusted) and then the solar generation is the cherry on top which will save money for you.

Similarly you might consider battery purchase in the same way and calculate an ROI based on the savings. Ive found that most savings are accomplished with just a small battery. 5kWh in my case. Fogstar sell very keenly priced batteries.

Posted by: @bontwoody

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Similarly you might consider battery purchase in the same way and calculate an ROI based on the savings. Ive found that most savings are accomplished with just a small battery. 5kWh in my case. Fogstar sell very keenly priced batteries.

FWIW I still cant make the case for a battery (if installed by a third party) stand up.  

I have gone down the tarrif route with 'manual' adjustments.  EON Next Drive gives 7 hrs of cheap leccy if you have an EV and is simple in the sense that all the cheap leccy is in one hit.  So schedule as much heavy use (eg washing machine, dishwasher, dehumidifier) as you can overnight, definitely don't do a setback, and you will save.

If you don't have an EV and don't have a heat pump that is supported by the OVO 15p offer (which I dont believe Samsung is at present), its a bit more difficult, compounded by the fact that the Samsung controller is a bit basic.  Octopus Cosy is the obvious go-to, but without a homely or battery and with the fairly basic Samsung controller, I cant quite see how to use it effectively.

@jamespa Similarly I cant make the case for another 5kWh expansion. However its difficult to quantify how much a small battery saves when using solar panels. The times when the sun goes behind a cloud for example. My gut feeling is that it might be quite substantial

I have to wonder if the cold lounge needs a much bigger, or additional, radiator to get sufficient heat output from water which is cooler than what the oil boiler would have produced. More emitter capacity should then enable a reduction in the flow temperature which is a key factor in achieving good, and economical, performance. The other rooms seem to be warm enough to accommodate lower flow temperatures. It may also be useful to invest in an infrared thermometer which can be used to check temperatures of radiators and look for cold spots in the walls. Wallrock thermal lining paper will make a small, but useful, improvement of the wall insulation.

Posted by: @jamespa

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Posted by: @bontwoody

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Similarly you might consider battery purchase in the same way and calculate an ROI based on the savings. Ive found that most savings are accomplished with just a small battery. 5kWh in my case. Fogstar sell very keenly priced batteries.

FWIW I still cant make the case for a battery (if installed by a third party) stand up.  

I have gone down the tarrif route with 'manual' adjustments.  EON Next Drive gives 7 hrs of cheap leccy if you have an EV and is simple in the sense that all the cheap leccy is in one hit.  So schedule as much heavy use (eg washing machine, dishwasher, dehumidifier) as you can overnight, definitely don't do a setback, and you will save.

If you don't have an EV and don't have a heat pump that is supported by the OVO 15p offer (which I dont believe Samsung is at present), its a bit more difficult, compounded by the fact that the Samsung controller is a bit basic.  Octopus Cosy is the obvious go-to, but without a homely or battery and with the fairly basic Samsung controller, I cant quite see how to use it effectively.

 

Same here @jamespa - we have a 12kW Samsung ASHP, solar and are currently considering adding a Tesla PW3, but no way do the numbers stack up financially.

We are currently on Octopus Cosy, and our average import price over winter was 19-20p per kWh, which worked out significantly cheaper than gas or oil for us. We make it work by using an overnight (midnight-4am) setback and reheating during the cheap rate 4-7am slot. We also bump up the heat in the cheap afternoon slot and then switch off during the 3h peak, but the house does get unpleasantly cold in the depths of winter (we can easily drop 3C in 3 hours).

A 10-13kW battery would allow us to run constantly at the Cosy cheap rate of around 13p, which means we'd be saving around 6-7p per kWh, which just doesn't add up considering the £8-9k cost of a PW3 installation. We would also likely use more electricity running constantly further eroding the value proposition. So we have taken a rounded view also considering comfort and usability, plus green / grid friendly considerations.

Solar can make a significant impact, particularly this time of year if it's sunny in the morning (when it's not cheap rate). Our 3.6kWp array can power the heat pump for much of the day, although sunny afternoons have less impact as cheap rate Cosy import is similar to the solar export rate. A large solar array can probably power a smaller ASHP even on a cloudy winter's day.