No mention of the _disadvantages_ I see; specifically - efficiency is related also to /flow/ temperature. Which is much lower than the gas boiler it might repl

No mention of the _disadvantages_ I see; specifically - efficiency is related also to /flow/ temperature. Which is much lower than the gas boiler it might replace - so you need big emitters (large radiators, Under-floor-heating) - and good insulation What might make 100% sense in a new build where you can design for these factors, but be awful in many existing homes.