A store that is open annually 6 days a week for 8 hrs each day (10:00 a.m. to 6:00 p.m.) is only occupied 28% of the year! That leaves more than 70% of the year for saving money when nobody is there to notice. Taking advantage of this opportunity to save energy means being sure lights and other systems are off or in their lowest acceptable settings, and using time clocks or programmable systems to assure that happens even when humans fail.
As these pie charts show, a typical retail store's electric use is heavily tilted toward lighting (almost 60%!). The only other significant energy user is the space conditioning, which accounts for 25% of the electric use and a whopping 80% of the gas use.
It's easy to see why lighting and space conditioning are the places to start with retail stores. Having lights on automatic timers, especially outdoor lights, makes sense. Indoor lights should be controlled as well. Even such a simple thing as a switchplate note asking employees and customers to turn lights off when not in use can be effective. An occupancy sensor or timer can work too for little used storage, rest rooms, and office areas. Because lighting is so integral to most retailer's businesses, it can be a touchy subject when it comes to areas with customer traffic. Highly efficient sources may not be good candidates where accent lighting to attract attention and creating a certain ambiance is considered valuable.
The larger opportunity may be space conditioning. In climates where cooling is the primary need, be sure the exterior windows are shaded or tinted to minimize solar heat gain. Many retail stores have glass covering the entire front of the store. The heat gain from these windows can be enormous and most often requires air conditioning to remove. Where heating is the primary need, being sure the system is efficient, that reasonable temperature settings are maintained and setbacks are used makes a big difference.
At the door, feel for air blowing in or out indicating the building pressure is out of balance. If there is a large rush of air either in to or out of the building when someone opens the door, consider some form of air barrier. Adding a vestibule or some form of air curtain can be expensive, but when you think that so much of the store's energy goes to heating and cooling, it may be cost justified.
And are the doors sealing well then they close or is there a large gap where they meet? Some changes are low-cost to no-cost, like adding some weatherstripping or adjusting the doors. Others will take professional help to analyze. As an auditor, you can be helpful by calling attention to problem areas.