I have 2 boilers and a space heater in my wash both Lochinvar, everything LP:
RWL-260 Bay Heat Boiler. 270,000 btu input
RBL-360 Floor Heat Boiler. 360,000 btu input
+ 100,000 btu space heater for the equipment room . < also LP gas.
So about 730,000 btu for everything when they are all...