By Jonathan Tan, VP Energy Services
The AMS Group, Hillphoenix
There are more than 152,000 convenience stores in the U.S. and about 80 percent of them sell gas. The food retail part of the business alone makes these stores energy intensive. Across the industry, food stores use an average of 51.5 kilowatt-hours per square foot – more than any other commercial building. For C-stores that sell gas, energy intensity can soar to as much as 94 kilowatt-hours per square foot or higher due to greater plug loads (e.g., coffee makers, slushy machines), outdoor lighting, and gas canopy lighting, all compressed into a relatively small footprint.
Not much can be done to reduce plug loads, but ample opportunities exist to cost-effectively improve energy usage for indoor and outdoor lighting and refrigeration, which together account for approximately two-thirds of C-store electricity usage.
A study of 50 C-stores with gasoline sales, prepared for the Minnesota Department of Commerce, identified the best opportunities for reducing energy consumption and increasing store profitability. Given the ubiquity of this format, it makes sense to look at these stores to understand opportunities in the C-store sector as a whole. Opportunities in refrigeration, interior lighting, exterior wall packs, and parking lot illumination pertain to C-stores in general, with improvements in gas canopy lighting relevant to 80 percent of this sector.
Although the study also looked at the effect of utility rebates on payback for energy improvements, audits identified several high-impact measures that could be justified by energy savings alone. These lie chiefly in adoption of LED lighting and refrigeration technologies, which tend to be underutilized.
Upgrade metal halide lighting to LED: The opportunities are in wall packs, parking lot luminaires, and gas canopy lighting.
Reduce wattage of interior lighting: Using 25- or 28-watt bulbs instead of 32-watt bulbs for T8 lighting provides adequate illumination and significant energy savings. Advancements in LED technology have improved performance and reduced cost, so converting standard fluorescent fixtures to LED may now also be cost-effective.
Replace cooler and case lighting with LED: Along with cost-effective energy reduction, replacing standard fixtures with LED lighting brings additional value. LEDs don’t depreciate in lumens in cold temperatures the way fluorescents do and so provide a better lit, safer environment for employees in walk-in coolers and freezers and better merchandising in cases. Grocery stores have long been benefiting from LED’s superior illumination and quick payback, and the opportunity is no different for C-stores.
Install occupancy sensors: These eliminate wasted lighting in such areas as restrooms and storage rooms.
Use floating head and suction pressure controls: Refrigeration systems are designed for the worst-case ambient conditions based on climate data for a store location. Floating head and suction pressure controls, which are underutilized in C-stores, take advantage of more typical ambient conditions, improving efficiency of low-temperature (freezer) and medium-temperature (cooler) systems.
Install anti-sweat heater controls: These monitor temperature and humidity in the store and pulse door heaters in coolers and freezers as needed to control condensation.
Upgrade fan motors to ECMs: Electronically commutated motors are energy efficient alternatives to evaporator fans in walk-in coolers and split capacitor and shaded pole motors in refrigerated cases.
In this study, these measures along with a few maintenance measures (installing strip curtains and cleaning condenser and evaporator coils), reduced electricity consumption by an average of 19 percent. At $0.11 per kilowatt-hour, the national average cost, this would mean savings of about $6,100 annually.
Energy Savings and Profit
Because profit margins are thin across the food-retail industry – about 1 percent for the industry overall and for the C-store sector specifically – even seemingly modest savings have significant impact on store profitability. The U.S. Department of Energy estimates that for food retailers a dollar saved in energy is equivalent to an $18 increase in sales.* For the average C-store, the efficiency measures identified in the study could have the same effect as increasing sales by approximately $110,000 a year.
*It’s often cited that saving $1 in energy has the same impact on the bottom line as increasing sales by $59. While the DOE has reported that equivalency in the past (see the ENERGY STAR Building Manual), the value has recently been revised to an $18 increase in sales.