aj_ok, welcome to the forum.  Your house is not too different to mine and we have just installed a 14kW Ecodan. It's hard to compare costs as we had new radiators and all pipework as we had no central heating.  Does your quote include a new hot water cylinder?

I would agree you should be in line for the maximum RHI payback. However, it is very unlikely an ASHP will be cheaper than gas at current prices.  You might achieve a COP of 2.5-3 over the year so you can work it out. Note that RHI is calculated using theorectical values from your ASHP spec and your EPC.  Speaking of which, you will need to get your loft insulated to 270mm and a new EPC done. 

Only you can say whether you'd be happy with the looks of the ASHP.  However, are you sure you can mount it on a wall? Ours had to be 300mm from the wall and it's mounted on rubber feet.  It's not especially noisy but I definitely wouldn't want it on the wall.  It's also heavy at over 130kg. 

I hope I'm not putting you off!!  It's early days for us but ours works very well.  You'll need to adapt a bit coming from gas as you say but our radiators still feel hot at 50 degrees, the house is nice and warm and there's plenty hot water. 

Welcome to the forums AJ.

The ASHP decision is never an easy or clear-cut one. I’ve found that ASHPs struggle for 6-8 weeks compared to gas/oil, but over a 12 month period, the are more efficient and cheaper than oil. Mains gas will still be tough to beat.

Your wife will need to adapt, as will you, because the slow burner ASHP is extremely different in set up to the ‘instant’ heat gas/oil boilers offer.

Nevertheless, if designed and installed correctly, you should be OK. 

As mentioned in a different post today, the heat emitter guide should be studied thoroughly - if rad sizes are correct, and the ASHP has been sized correctly, the system will work.

From what you’ve described, the price is reasonable. Did they provide you with a heat emitter guide? 

Thank you both for the welcome and replies.

As yet its early stages and we had a technical survey done today and a follow up chat arranged for next week, hopefully when we know more Inc an emitter guide, otherwise I will ask.

Also to mention the install will Inc all trvs on all new rads (all exc the designer once are imperial measurement single panels with no trvs) 

The wall mount was a suggestion from them, otherwise it'll be on the rear, which I don't fancy cold air pumping out onto the patio area. 

Will keep posted, thank you again for your replies and knowledge and experience sharing in various threads. 

thanks again for the replies.

Struggles to get the 'paperwork' from the company, seemed very reluctant to provide prior to me picking an install date.

All rads have been advised to change, not sure im keen on a large K3 in the dining room (for decor purposes). 

Cost is predicted to be >£200 more than current payments.

The only docs i have been sent attached for thoughts (i know nothing in respect to the expected RHI etc. 

Two things to note, my electric is actually 13.45p for 19 hours, 5.5p for 5 hours (they used the day rate without vat). Also disparity on each doc regards the pump, although i think its the mitsu 14kw that will be used.

Welcome any thoughts, im still not overtly convinced and not sure can cope with replacing the designer rads with larger k2/k3

Your energy demand is v similar to mine. I didn’t have to change radiators (yet)

I would suggest getting alternate quotes from different suppliers

Does your price include the radiator replacements?

That's rights Julian, all the parts and labour, inc all rads/towel rails and manual TRVs

Tank in loft (current is in a landing cupboard)

I have microbore piping downstairs and 15mm piping upstairs, not been told this is an issue/factor in anything, but having seen a review im further sceptical https://uk.trustpilot.com/reviews/6042273cf85d75064c3859ee

Hi aj_ok, a few observations/questions based on my experience.

• the price looks OK; it's similar, if maybe a little less, than mine considering the number of radiators and the fact you have MMSP.
• these are some big radiators.  The 1800x700 K3 especially is huge. And is your kitchen especially large?  Again that's quite a big rad. 
• Is your ASHP 14kWh (as stated on page 1) or 11.2kWh (as stated on page 2).  Ours is 14kWh and our rads are nearly all smaller than yours.  4 of ours are 1000x600 K2s, biggest is a 600x1400 K2 and we have no K3s 
•  Page 2 says 19016 heat and 3278 HW.  Is that from the EPC?  If so it's very close to ours.  Do you know what the "energy potentially available for RHI" of 14,550kWh is?  I thought RHI was calculated on the EPC number (capped at 20,000). 
• You shouldn't count on the running costs predicted.  Page 3 says you'll consume 7000kWh; if your need is 22,200kWh that's a COP of nearly 3.2; you probably won't achieve that over a year (I'm aiming for more like 2.7)
• Is your cylinder going to be big enough?  Ours is 250l but it depends on how many of you there are. 

I think you definitely need to ask some questions and/or get another quote.  It feels like mixing pipework bores is going to make things harder for the ASHP but I really don't know.

If you want to check the radiators there are online calculators like this one.

http://starsapp.co.uk/basic-heat-loss-calculator/

Kev

So early days for me aj. According to my installer, 10mm micro bore are ok if your main system/loft pipes are at least 28mm. Ideally 35mm. Mine are. Only the drops to each radiator are 10mm. Check yours. Most installers said I had to change my 10mm which was a “no” from my wife. So the system was designed around that constraint. If you can change them out, the pump speed can be reduced, lower HP temperature and hence better COP. 
Your quoted price looks pretty good if they are changing radiators 

Good spot Kev M. 
Aj, what is the room by room heat demand / loss calculation?  As Kev M says, changing every radiator is surprising. Can you do work to reduce heat loss?

The 1800x700 K3 especially is huge. And is your kitchen especially large?  Again that's quite a big rad. 

That is an exceptionally big radiator - we have a 1200x700 K3 in a very cold 6x6m room and it heats it adequately now. Same question as Kev - how big is the kitchen? 

Mixing pipe bores appears to have affected our flow rate to the coldest room mentioned above – this was remedied by putting in a larger, more powerful circulation pump, but the real fix for us was putting in the aforementioned K3 rad in that room. Despite the low flow, the heat that gets there now does heat the room. Maybe that's the installer's rationale - engineer and factor out the varying pipe bore. 

Can't really add much more than what @kev-m has stated above - very thorough Kev.

I'll conclude by recommending you get another quote (or two) – this is critical @aj_ok - we got five or six quotes before puling the trigger because it really does allow you to evaluate what's really needed specifically for your property.

Hi @aj_ok !

Have you ordered the work from Greener Living?

They are currently trying to convince us for an installation. I'm all in favour of it, just trying to do the due diligence about the company.

They've got quite good rating on Trustpilot with some terrible reviews, too.

We have a 3 bed bungalow with storage heaters all over the house.