A large portion of a building's electrical costs usually comes from lighting, but the operating cost of commercial lighting includes more than just energy use. Much of a lighting system investment is made in consumable components (hardware such as lamps and ballasts) with a known life expectancy and cost. Regular replacement also requires labour, which also must be considered.
A comparison of an existing system and a replacement system based only on capital investment and energy savings would not be complete, since it would not consider the differences in ongoing maintenance costs between the two installations. Quite often the energy efficient lamps and ballasts will cost more than the equipment they are replacing; therefore, this added maintenance cost will partially offset energy savings.
This effect is included in the relevant lighting reports and is carried forward when all of the lighting retrofits for a facility are rolled up and stored as a single Opportunity using the Roll Up Lighting Opportunity feature.