Commercial and institutional buildings energy use and expenses differ significantly from residential. The typical residential electric bill is based on monthly usage and not the intensity of usage at any one time while the commercial customer electric bill is often largely based on the amount of energy intensity that they used.
There are many opportunities to save energy in commercial buildings. In new construction, the site can be chosen so as to maximize opportunities to face to the north or south, away form direct sun. If there are many tasks needing lighting, the use of daylight can be incorporated into the design. Windows can be selected to maximize the visible portion of the spectrum of sunlight while reflecting the non-visible portion. Commercial buildings with high occupancy such as offices, schools, and public buildings often require cooling through most of the year because the people and associated activities put off heat. Choosing an appropriate cooling system for removing heat and moisture is important. In humid climates the key factor in design of such systems is the amount of outside air brought in for ventilation. Lighting systems should complement the day-lighting system, and a roof system that rejects the heat is extremely helpful. Once the construction is complete, the building should be commissioned to verify that it works as planned