What the buffer tank is for
The buffer tank gives the circuit water volume. Without it the heat pump starts and stops constantly to hold temperature, and that short cycling is what wears out the compressor and pushes consumption up. With enough buffer the machine runs in long, steady cycles, which is where a heat pump performs at its best and where you actually see it on the bill.
Manifolds and balanced circuits
Every circuit in the house leaves from the manifold. Balancing them means sharing out the flow so the far bedroom reaches temperature just like the room next to the plant room. Without balancing, people compensate by raising the flow temperature for the whole system: the entire house burns more energy to fix one room. That adjustment is made at commissioning, with the system running.
The wiring is installed with tomorrow in mind
The panel and cable runs look the way they do because in six years somebody will have to open them. Circuits identified, cable gathered, room to get a hand in. A tidy plant room is diagnosed in minutes; a tangle of cable turns any service visit into a full afternoon that you end up paying for.
Insulation: the efficiency you cannot see
Manifolds and pipework are insulated. Every bit of heat that escapes between the machine and the radiator or the underfloor loop is energy you have paid for that ends up warming the plant room. Across a whole winter of daily operation, that invisible detail is one of the ones you notice most. Brass valves and first-grade copper, because this room has to last as long as the house.