What is the most efficient central heating system to install?
The most efficient central heating option by a large margin is a central radiator system with cogeneration heat as the energy source. A central fan coil unit system with cogeneration heat is a close second.
If cogeneration heat is not available, or if it could only provide a small proportion of the heating needed, then individual heating by gas fixed flued heaters or heat pumps (reverse cycle air conditioning) in each dwelling are the next most efficient choices. Gas-driven air conditioners score better than all but the most efficient electric air conditioners.
A central variable refrigerant volume (VRV) system provides efficiency similar to having air conditioners of the same coefficient of performance (COP) in each dwelling. It has the advantage of centralised 'outdoor' units, but disadvantages of some limitation of piping length, challenge of apportioning energy costs (though some manufacturers have control systems that can assist in this) and a potential risk of excessive refrigerant concentration if a leak develops within an apartment. Again, gas-driven VRV systems score better than electric systems.
Other central systems are unlikely to be practical for small developments of less than about 50 apartments, and all have the challenge of apportioning energy costs. Radiator and fan coil unit systems with gas boilers are more efficient than water source packaged units.
A water source packaged unit system with electric or gas driven heat pumps as the energy source scores better in BASIX than one with a gas boiler.
All systems with electric boilers or electric resistance heating score poorly in BASIX.