The important thing to remember for heat pumps is they don't work well if the outside temperature drops below about 40F (about 4C). I have a dual gas/heat pump system which gives pretty good results.
... they also rely on electricity supply, about ~25% of the heat shifted is consumed in electricity for the best efficiency pumps.
... if it is mission critical to keep the heat flowing probably plan on back-up generation in case of main/grid electrical failure