Actual operating schedules vary widely for any given building type, and tabulated average values
provide more approximate estimates with larger variations than values for fixture wattages. Also,
tabulated HOU values are given for entire buildings, not by usage groups within buildings. The
protocol requires HOU estimates be entered into the inventory by usage group, which will vary
from the building average. For these reasons, the protocol recommends use of building-specific
lighting operating hours, when these are available, supplemented if necessary by tables of HOU
values.