Py allows producing steam from water. Unlike vanilla, Py has a variety of temperatures of water. The energy required to boil water depends on its current temperature. YAFC appears to not account for this.

A common process in Py is to condense excess cold steam (150 degrees) into 99 degree water, then boil this water into 250 or 500 degree steam. YAFC appears to calculate the fuel consumption for doing so on the basis of using 15 degree water, leading to a drastic over-estimate for fuel consumption.