Help with heating choice, LPG to ASHP??

vessy Posts: 6 Forumite
edited 23 January at 3:23PM in Heat pumps

I will soon be looking to extend my house, this will include moving/replacing an old floor standing boiler. We have no main gas supply in the village and currently use LPG @ 44ppl. I have read many stories about ASHP & GSHP but sometimes the cost reported to run them seems nearly as high as i'm paying now. House is late 1960's, cavity wall insulated, new double glazing and loft double insulated (approx 10-12").

Currently have radiators for heating, all of these are new and of the modern high efficiency type and oversized as we have a single pipe system with swept T's, I know heat pumps don't favour this system but I currently run the LPG boiler at around 60 deg and the house gets plenty warm (21-22 deg)

Would you agree that my following calculations are valid?

Last year 2650 litres of LPG were used which roughly equates to 18550 kWh & £1166 cost (some of this for a gas hob but ignored this)
Sedbuk rating for current boiler is 75%, so around 14000 kWh were needed to heat the house.
ASHP system working at around 55 deg (i'm assuming an average COP of 2.5) would use around 5600 kWh of electricity
Currently pay 7.73p kWh so annual cost of £433, currently saving me £733.

Don't want to outlay loads of money on ASHP if i'm not going to save anything, could just fit electric boiler for £700 and save me £80 per year!

According to the boiler sizing wizard on energysavingtrust web site I need just over a 10kW boiler.

Am i way off the mark? Should I expect a lower COP from ASHP @ 55 Deg?


  • how about fitting a modern LPG boiler with an efficiency of >90%? That would save you 15%...
  • vessy
    vessy Posts: 6 Forumite
    Thought about that too, only worry is the ever increasing price of LPG!

    Also, as it's a 1 pipe system, flow and return temps are a lot closer together than a conventional 2 pipe system, doesn't this effect the efficiency in modern condensing boilers in a bad way?
  • ra200
    ra200 Posts: 172 Forumite
    Lpg costs seem to being going up very quick and in 5 years time just think of the price of lpg i would go for a good ashp as long as it is the right size and has a good rep and you have good insulation you you will be fine,
  • HappyMJ
    HappyMJ Posts: 21,115
    Combo Breaker First Post
    Don't fit an electric boiler (my opinion only) you'd need 14,000 kw at 7.73p so it'll still cost you £1082....not worth the capital cost of changing. I'd fit either a more efficient LPG boiler when this one packs it in or an ASHP but ASHP's are loud and have other disadvantages you need to consider. A COP of 2.5 is fine many claim it's higher.

    If you want to save money then turn the thermostat down. 21-22 for me would be tropical i'd be sweating loads at that temperature...and I'm originally from a hot country...
    :p Regular savers earn 6% interest (HSBC, First Direct, M&S) :p Loans cost 2.9% per year (Nationwide) = FREE money. :p
  • vessy
    vessy Posts: 6 Forumite
    The only advantage of an electric was the instal being easy and size (inline unit) Would love to fit GSHP but the cost really puts me off. Agreed ASHP have many factors to consider, however by my calculations it should provide a huge cost saving.

    21-22 is warm, well I think so, shame the wife doesn't! Normally run 19-20.

    What price should I expect for a GSHP install with a bore hole? Using existing radiator plumbing?
  • I am in the same situation, but in France. LPG is even more expensive here, and the price goes up whenever they feel like it, and they think of a figure then double it. I prefer oil in the sense that the price is much more transparent - it varies regularly by small amounts. LPG is quiet for a few months, then wham, up 10%.

    I used to be a global diesel and jet fuel trader for Total (10 years) so have enough experience to be fairly certain that these prices are going up and sharply. The monthly increase in demand from China, India, etc. is phenomenal. For every litre we save they consume 3 more.

    We have 5 gites in Finistere and we are in the process of ditching anything oil related. Our main house (600m2) is heated by a 44kW Guntamatic log boiler (fantastic), and log burners are going into the others.

    The LPG house is going to get a 10kW Sdeec stainless steel heat pump. COP at 7'C/35'C (the standard I believe) is 4.3. I reckon we should save a good 1000 Euros a year which gives us a 9 year pay back. It would be better if the house were lived in more in the winter, but it isn't.

    In any case, the LPG boiler looks creaky these days, so I reckon it would need replacing soon anyway.

    We have to have the buried LPG tank dug out at our cost, which will leave a nice big hole, but I say good riddance!
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