Two common metrics for measuring paper drying efficiency are drying load (amount of water evaporated per hour) and steam consumption (amount of steam used per hour). The Technical Association of the Pulp and Paper Industry (TAPPI) recommends these metrics be indexed by the dryer surface area (resulting in pounds of water evaporated per hour per square feet of dryer surface area) and by the amount of water evaporated (resulting in pounds of steam per hour per pound of water evaporated). The indexed values are better indicators of dryer performance and overall energy efficiency of the drying process. Indexed values can be compared to similar machines as a benchmark of performance.