oil boilerAn oil-fired boiler (hydronic system) uses the same type of burner as an oil-fired forced-air furnace, although a boiler is often somewhat smaller and heavier. There is no circulating fan and filter housing as with a forced-air system. Instead, most boilers require a circulating pump to push heat around the house through the pipes and the radiator system. The seasonal efficiency of old conventional hydronic systems is similar to that of conventional forced-air systems, which is around 60 percent. However, there are many options for efficient oil fed boiler systems.