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wbandrews
Hi I have a three bore hole GSHP rated at 8kw heat output . It feeds a radiator system with radiator surface temp. of around 45deg C. I used to have a bulk propane system heating the radiators and annual cost was around £800 per anum probably nearer £1000 at todays prices. The secret to success of radiator based GSHPs is to ensure that at the lower surface temperatures the radiators have enough area to work efficiently. Typically they need to have twice as much area as one working at 80deg C( fosil boiler temp.). The numbers are as follows . For 1 kw into your GSHP you will get somewhere beteen 3.5 to 4 Kw out. The figure of 4K is for underfloor lower temp systems. Installed cost for mine was £6000 but running vosts are now 50% of the old propane set up. Your carbon footprint is also 50% less if you acheive the 1 to $kw ratio as most fossil powered electricity power stations are less than 50% efficient.
Therare a number og good UK companies making heat pumps in the UK , not imports.