Retail buildings in the U.S. use an average of 14 kilowatt-hours (kWh) of electricity and 31 cubic feet of natural gas per square foot annually. In a typical retail building, lighting, cooling, and heating represent about 60 percent of total use (Figure 1), making those systems the best targets for energy savings.
When trying to better manage your building’s energy costs, it helps to understand how you are charged for those costs. Most utilities charge commercial buildings for their natural gas based on the amount of energy delivered. Electricity, on the other hand, can be charged based on two measures: consumption and demand (Figure 2).
The consumption component of the bill is based on the amount of electricity in kWh that the building consumes during a month. The demand component is the peak demand in kilowatts (kW) occurring within the month, or, for some utilities, during the previous 12 months. Demand charges can range from a few U.S. dollars per kilowatt per month to upwards of $20 per kilowatt per month. Since it can be a considerable percentage of your bill, care should be taken to reduce peak demand whenever possible. As you read the following energy cost management recommendations, keep in mind how each one will impact both your consumption and demand.
Almost all of the conservation measures we discuss here represent good investments. Most will not only save you money but will also enhance both the aesthetics of your store and the amount of merchandise it sells.
Many stores can benefit from quick low-cost/no-cost energy-saving solutions, such as turning things off, turning things down, and keeping up with cleaning and maintenance.
Turning things off seems simple, but remember that for every 1,000 kilowatt-hours (kWh) you save by turning things off, you save US$100 on your utility bill, assuming an average electricity cost of 10 cents per kWh.
Lights. Turn off lights when they are not in use. Occupancy sensors and timers can help, but a less expensive alternative would be to develop a standard store-closing protocol for shutting off lights during closed hours.
Electronic displays. Many stores have electronic displays that are left on even when the store is closed. Consider shutting off the displays during closed hours, either manually or with simple timers.
Doors. Many retail outlets keep their doors open on hot days, with the air conditioner running, as a way of attracting customers. However, that practice can increase air-conditioning costs significantly, and in some jurisdictions, it can leave retailers subject to fines. Alternatives to an open door include posting a sign that says that it’s cool inside, or installing two sets of doors and leaving only the outer one open.
Some equipment cannot be turned off entirely, but turning it down to minimum levels where possible can save energy.
HVAC temperature setbacks. During closed hours, turn temperature settings down in warming seasons and up in cooling seasons.
Peripheral and back rooms. Make sure that HVAC settings in stockrooms, offices, and other peripheral rooms are at minimum settings.
Making sure that your HVAC system is regularly cleaned and serviced can help prevent costly heating and cooling bills.
Check the economizer. Many air-conditioning systems use a dampered vent called an economizer that draws in cool outside air when it is available to reduce the need for mechanically cooled air. If not regularly checked, the linkage on the damper can seize up or break. An economizer that is stuck in the fully open position can add as much as 50 percent to a building’s annual energy bill by allowing hot air in during the air-conditioning season and cold air in during the heating season. Have a licensed technician check, clean, and lubricate your economizer about once a year, and repair it if necessary. If the economizer is still operating, have the technician clean and lubricate the linkage and calibrate the controls.
Check air-conditioning temperatures. With a thermometer, check the temperature of the return air going to your air conditioner and then check the temperature of the air coming out of the register that is nearest the air-conditioning unit. If the temperature difference is less than 14° Fahrenheit (F) or more than 22°F, have a licensed technician inspect your air-conditioning unit.
Change the filters. Filters should be changed periodically - every one to six months, depending on the pollutant loading from indoor and outdoor air. More-frequent changes may be required during the economizer season, because outdoor air is usually dirtier than indoor air.
Check the cabinet panels. On a quarterly basis (or after filters are changed), make sure the panels to your rooftop air-conditioning unit are fully attached, with all screws in place and all gaskets intact so that no air leaks out of the cabinet. Chilled air leaking out can cost $100 per rooftop unit per year in wasted energy.
Clean the condenser coils. Check the condenser coils quarterly for either man-made or natural debris that can collect in them. At the beginning and end of the cooling season, thoroughly wash the coils.
Check the airflow. Hold your hand up to the registers to ensure that there is adequate airflow. If there is little airflow, or dirt and dust are found in the register, have a technician inspect your unit and ductwork.
Longer-term solutions should also be considered. Although the actions covered in this section require more extensive implementation, they can dramatically increase the efficiency of your facility, and can even improve the shopping environment at the same time. Ask your local utility representative for more information about incentives for such projects.
Commissioning is the process of ensuring that systems are designed, installed, functionally tested, and capable of being operated and maintained according to the owner’s operational needs. Doing so can cut energy bills by 10 to 15 percent or more, and often provides a simple payback of under 1 year. When this process is applied to an existing building that has not been commissioned before, it is called retrocommissioning. When it is applied to a building that has been commissioned before, it is called recommissioning. Recommissioning is recommended every three to five years to maintain top levels of building performance. In another type of commissioning—ongoing commissioning—monitoring equipment is left in place to allow for ongoing diagnostics.
Building automation systems (BASs), sometimes called energy management systems, save between 5 and 15 percent of overall building energy consumption, and can also improve occupant comfort. Older or poorly maintained buildings can also benefit greatly from a BAS retrofit, sometimes yielding savings of over 30 percent.
Lighting is critical, both in creating an ambiance and in making the merchandise attractive to shoppers. High-quality lighting can reduce energy bills and drive higher sales.
Display lighting. Proper display lighting is critical for driving retail sales and preventing merchandise returns. Quartz halogen lamps are commonly used for accenting merchandise because they provide a bright, focused column of light with excellent color quality. More efficient alternatives include compact fluorescent, metal halide, and LED track or spot lights. Retail accent lighting is a growing area for LEDs because they provide the ability to vary color, create sparkle, and aim the light precisely. Have a lighting consultant review your lighting layout to ensure that it provides the appropriate light levels, quality of light, color rendering, color uniformity, and energy efficiency.
Fluorescent lamps. If your facility uses T12 fluorescent lamps or commodity-grade T8 lamps, relamping with high-performance T8 lamps and electronic ballasts can reduce your lighting energy consumption by 35 percent or more. Adding specular reflectors, new lenses, and occupancy sensors or timers can double the savings. Paybacks of one to three years are common.
Big-box retail stores with high ceilings might consider going to a system that uses T5 or T8 lamps to boost both lighting quality and efficiency. These lamps are more energy-efficient, offer better light quality, and are easier to dim or control with occupancy sensors than the high-intensity discharge lights that are typically found in high-ceiling stores.
Smart lighting design in parking lots. Parking lots are often overlit—an average of 1 foot-candle of light or less is usually sufficient. The most common lamps used for outdoor lighting are high-intensity discharge (HID) sources—metal halide and high-pressure sodium. In recent years, fluorescent lamps, compact fluorescent lamps (CFLs), and induction lamps have also become viable sources for outdoor lighting, offering good color quality and better control options than HID sources. Light-emitting diodes (LEDs) are also rapidly becoming a good choice because they can reduce light pollution while offering efficiency and long life. LEDs are expensive but costs are decreasing and performance continues to improve. Dimming and occupancy-sensing controls can also lead to energy savings in parking lots.
Security lighting. Using occupancy sensors with outdoor security lighting can save energy and improve security.
Daylighting. Daylight can improve the ambience of a store and reduce the need for electric lighting. Some evidence suggests that daylighting can also lead to increased sales. Dimming ballasts and photocontrols can be used to reduce the amount of electric light used when daylight is present.
LED signage. LEDs used in exit signs, “open” signs, and other applications can cut energy costs and also reduce maintenance costs compared to incandescent, CFL, neon, and other options.
When only a few people are in a store, energy can be saved by decreasing the amount of ventilation supplied by the HVAC system. A demand-controlled ventilation (DCV) system senses the level of carbon dioxide in the return airstream and uses it as an indicator of occupancy. DCV can save energy during peak cooling periods when many shoppers are at work and occupancy is low. In retail sales applications, DCV works best when a dedicated HVAC system serves the sales floor.
If the roof of your building needs recoating or painting, consider white or some other highly reflective color to minimize the amount of heat the building absorbs. This change can often reduce peak cooling demand by 15 to 20 percent. For a list of suitable reflective roof coating products, check out the U.S. Environmental Protection Agency’s web site.
Modern, specularly selective glazing makes it possible to maintain good visibility through a window while limiting solar gain, which can heat a store and fade clothing colors. If your store is in a warm climate, replacing clear glazing with more sophisticated glazing can be done with short paybacks and can result in increased comfort for shoppers. Specify new glazing carefully—you may need to seek a different solution for each facade. Applying specularly selective window films to existing windows may allow you to achieve some of the same benefits as new glazing, but at a lower cost.