A case where the boiler is not used can arise but one has to look for it, since HOMER only ranks by NPC.  It would be simpler not to have the boiler in the first place. Is it possible?

 

Unfortunately, for systems containing a thermal load it is not possible to get rid of the boiler.  We hope to remove this requirement in a future version of HOMER, but for now the simulation logic assumes that it can always rely on the boiler to serve any thermal load that the rest of the system does not serve.

You can, however, probably accomplish what you wish by making the boiler very expensive so that HOMER avoids using it.  The boiler will appear in the schematic, but if it is expensive enough and the system has other ways of serving the thermal load, then HOMER will not use it, and it will have zero cost.