High Efficiency Boilers
Mod-Con or modulating-condensing boilers are the current standard for high efficiency natural or propane-fired space heating boilers. Modulation then allows for less-than-full-fired operation at thermal efficiencies (the burner flame actually goes up and down controlled by water temperature demand) in the mid to high 90s% (many reaching 95% AFUE!). Old-fashioned low efficiency (88% or lower) boilers are full-fire (a few actually fire in two stages) but can’t be controlled to the same extent o
