Homeowner has a very old boiler, showing former use of coal before it was converted to natural gas. Online, I read that even these old boilers were not so inefficient. 70-80% seasonal efficiency, depending on how badly oversized the system is. Does anyone have different understanding? One peculiarity, one can hear the boiler pilot light running, and the gas consumption is relatively high in summer at ~50-60 Therms. (Could be due to hot water and cooking...?). 2 residents, 1500 sf house in Western PA. Is there some possible recommendation to shut down the boiler completely (including pilot) for summer months?
If the boiler is not also heating domestic water, then do shut it down. Shut off the gas valve as well.
It should also be set for a cold start, only firing up when there is a call for heat.