I had two questions on steam use this week.

Steam use depends on how much water is evaporated.  This can be estimated from the volume dried (in cubic feet or meters, not board feet) and the moisture content change.  It will vary with the specific gravity of the species.  The attached Excel sheet will calculate the water removed.

Estimating steam use requires an assumption about kiln efficiency.  50% efficiency is not a bad guess if you have no idea.  Well insulated, well sealed kilns operating on a fast schedules will probably be more efficient than this.  A poorly insulated kiln on a long schedule with lots of steam spray will be less efficient than 50%.  The attached Excel sheet will also estimate steam use.