A building is not a thing, but a set of systems. As with any system, it can be difficult for observers to identify how each facet impacts the whole. A building owner or manager looking to reduce their energy footprint may have a tough time identifying where their electricity, natural gas, and other fuel sources are going, particularly in a building with no sub-meters. What follows is a general look into how commercial buildings operate in the United States, geared toward helping Property Owners, Managers, and occupants understand how their decisions and habits affect the overall energy footprint. The most crucial time period for a building in terms of its energy efficiency is the design phase. With a pre-existing building you already have a set threshold of how well your building can perform given the technology and infrastructure it was constructed with. This does not, however, mean that you are unable to create positive change. There are a number of measures you can put in place and alterations that can be made to building operation to significantly decrease its energy footprint.