Hi @Mike H.

Welcome to the forum. I don't now have a similar property myself but I can say that our annual energy requirement was surveyed at 13,000kwh and that we have a 14KW Ecodan. So potentially the 12KW Samsung might be a bit on the small side.

The main thing to be aware of is that your energy requirement will be very heavily concentrated in a few months of the year (over winter) and that it is at lower temperatures that the ASHP are least efficient in terms of the COP. So potentially you could assume that an average COP of 3 would be as good as you might achieve. 21,000Kwh at an average COP of 3 equates to 7000+KWh electricity consumed.

The other thing to consider is that ASHPs work best by running continuously and keeping the whole house at a consistent temperature. Because of the low flow temperatures, the response time can be very long and as such, they are not really suited to letting rooms get cold and then try to heat them back up again say between 6-8am in the morning.

We came to our current house from an old farm, with an oil aga and oil boiler with radiators and it has taken me a long time to retrain my brain to operate with an ASHP.

@mike-h,

Welcome to the forum. I agree with what @hdj says; ASHP heating is more of a slow and stready approach rather that heating up/cooling down.  That's especially true with your house, which will have a high thermal mass and will take a long time to heat up.  Do you know how much gas you're using for heating/HW now?  As you say Agas use a lot of energy and getting rid of yours will save a lot of money.  We inherited an electric one and it only lasted a few months.

Another point is that 170l is quite a small cylinder. How many occupants is it for?

There is no reason why a well designed ASHP system won't work for you.  It sounds like you have insulated as much as you can as an end terrace you have the advantage of sharing your neighbour's heating on the shared wall.  Your kitchen sounds a little problematic but should work if you can accommodate the right sized radiator. 

Kev 

Hi Mike, we have a 210m2 stone cottage that sounds similar to yours with thick walls and mostly tiled floors. It works well but we have a single story extension at the far corner of the property that gets cold very quickly (a bit like your kitchen) as it has minimal insulation and an elevated airy ceiling. We just maintain a low temp of 16-17 in there and use a portable radiator for a quick economical boost if we use it in the evenings. The ASHP does work very well in there to be fair, but our concern is that due to the length of run for the pipes to get there and the poor insulation, we will be spending huge amounts of cash keeping a room warm we rarely use. 

The installation costs sound reasonable and we get pretty much that RHI back for ours - the difficulty is getting a decent installer in all done and dusted before next April. I have made a thread about my installation if you get bored "My Shropshire ASHP installation" which is in the main ASHP section. We have a 16kw ASHP which does seem to work well although it really struggles with a couple of rooms through no fault of its own - the previous owner fitted UFH throughout (to a crazy logburner/thermal store system that never worked) and decided elevated wooden floorboards/UFH was a sensible installation for a couple of rooms.

Hence those rooms do take a long time to get warm and really need replacing with tiles. The combination of tiled floors and UFH we have downstairs otherwise works really well and walking in socks over a warm floor is an absolute delight, our upstairs radiators get pretty warm too and whilst they are never 'red hot' like you get with gas/oil, they are warmer than you might think and keep the bedrooms pretty toasty. I was worried that the low temps would see the ASHP go nuts and struggle but it's coped well, some advice I had was to 'help' the ASHP by boosting it before a cold snap comes and I can see the wisdom in this. The bills haven't been too crazy either yet despite some really bitter nights. Good luck!

@hjd  Many thanks for your comments. I think that getting used to keeping the house warm most of the time may be a big change for us. Because we don't do that at present, it is difficult to know what our real gas usage would be. The figures that we have been given suggest that we would be using just over 7000 kWh of electricity, but the assumption used for that calculation is that the outside temperature is -2.8 for 6 months of the year. Therefore we have been told to expect much less in the real world. Even if we do use 7--10,000 kWh per year that is less than we are using at present even without heating the building during the daytime, so it must be a good thing for the planet at least.

@kev-m Thanks for your encouragement. We use about 14,500 kWh of gas per year, of which probably 30-40% is from running the Aga over winter. When my father in law lived with us, we were using more like 32,000 kWh per year. We kept the rooms much warmer in those days. There are only two of us now, so hopefully the cylinder size will be OK. A friend of mine has a two stage Daikin ASHP which can provide higher flow temperatures and I wonder if that would be more suitable if running lower temperatures during the day and higher in the evening?

@siko Thanks for some very helpful comments. We feel a lot happier about taking the plunge from reading all the responses. You obviously inherited a very strange heating system and had a pretty eventful journey installing your current one. We have a couple of air bricks where there were fireplaces in the bedrooms and these are quite draughty. I think I need to take some advice on how best to ventilate the chimney while minimising the draught.

Posted by: @mike-h

@siko Thanks for some very helpful comments. We feel a lot happier about taking the plunge from reading all the responses. You obviously inherited a very strange heating system and had a pretty eventful journey installing your current one. We have a couple of air bricks where there were fireplaces in the bedrooms and these are quite draughty. I think I need to take some advice on how best to ventilate the chimney while minimising the draught.

Hi Mike, yeah draughtproofing is absolutely essential for an ASHP. Because we had the logburners on semi-permanently the draughts were never a massive issue as the house got warm very quickly with them going (although not everywhere). We had 5 airbricks, some of which were essentially a 5" hole to the outside with no grille or restriction - you can imagine what the draught was like through there on a cold, windy day! I have sealed up all bar one of the airbricks and the difference is staggering - we had a double airbrick that I left open but fitted a grille to - even with that closed there is still a small draught and the wall/floor around it gets bitterly cold, so I will need to seal that too. Our windows and doors were fitted really badly with lots of gaps (I think the previous owner did them 🙁 ) and installing brush seals around the worst of it has made a massive difference too, it's pretty cheap and easy to apply as long as you can still close your door. I think there is a lot of advice on here to sort insulation/draughtproofing before you fit an ASHP and it is spot on - our costs are reasonable but I can tell you we would be paying a ridiculous amount right now if I hadn't sorted the draughts and I bet the house would still be cold - as it is we have a toasty warm house...at last.