In a nutshell, the savings are "virtual" (you will save on gas and electricity bill but need to pay the heat pumps, solar panels and the water deposit + the needed works) the (calculated, possibly a bit optimistically) break-even point is around 20-25 years, the expected life of the heat pumps being stated as 15 years.
So there is the need of incentives/financial aids from the state.
And all this may apply on an "ideal" self-standing home (not particularly common at least in Italy and Spain AFAIK) that has enough roof surface for the panels, has space for the heat pump radiators and for the hot water tank[0]).
[0] a 400-600 lt hot water tank is "huge" (and heavy)
So there is the need of incentives/financial aids from the state.
And all this may apply on an "ideal" self-standing home (not particularly common at least in Italy and Spain AFAIK) that has enough roof surface for the panels, has space for the heat pump radiators and for the hot water tank[0]).
[0] a 400-600 lt hot water tank is "huge" (and heavy)