A1. The efficiency of a centralised or communal system depends on the technology being employed to generate the heat.  The basecase would be a boiler only scheme, which, using modern plant and pipe systems might be marginally more efficient than the individual systems due to better control, reduced cycling and effective condensing of flue gases.
However, more commonly, communal systems are considered as a means of deploying combined heat and power (CHP) or some other low carbon heat generation plant.  In this case the overall efficiency of the system needs to be considered and a calculation of comparable CO2 emissions undertaken.  Electricity generated by CHP plant offsets grid electricity and this needs to be taken into account.  Typical CO2 savings from a communal CHP led system when compared with individual boilers would typically be in the range 5-20%.  If renewable fuels can be used the savings can be much greater.
 
There are many other reasons why communal systems can be more advantageous than individual including: 
  • economies of scale – it can be cheaper to install a communal system than individual systems   
  • reduced maintenance – instead of having multiple individual boilers to maintain, the communal boilers can be maintained centrally and regularly.  Central communal systems with a planned maintenance programme will operate more efficiently in the long term than individual systems which are less likely to be regularly serviced by individual owners.
    reduced fuel costs –  communal systems allow bulk purchasing of fuel which is lower cost.  The management organisation may also seek to enter a fuel purchase agreement where the price is fixed for a period of time.  This allows for longer term fuel price security.
  • adaptability –  a communal system can allow for future integration of new technologies (e.g. renewables), fuel switching or connection to a wider district heating scheme.   It is not cost effective for individual systems to link to district heating schemes in an ad hoc way and the use of renewable fuels or technologies at the single dwelling level is often impractical and less cost-effective than for communal systems.