Grocery stores in the
Average energy-use data
You’ll be better able to manage your store’s energy costs if you understand how you’re charged for energy. 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 how much electricity, in kWh, 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.
Monthly demand charges can range from a few dollars per kW to upward of $20 per kW. Peak demand can be a considerable percentage of your bill, so take care to reduce it whenever possible. As you read our recommendations on managing energy costs, keep in mind how each one will affect both your consumption and your demand.
Turning things off
It’s the simplest of ideas and doesn’t require much more than staff training. Remember that every 1,000 kWh you save by turning things off equals $120 off your utility bill (assuming average electricity costs of $0.12 per kWh).
Plugged-in devices Shut off computers, cash registers, bar-code readers, deli scales, and deli cooking equipment when not in use. Smart power strips that have built-in occupancy sensors can shut off plugged-in devices after a set interval of inactivity.
Lights Turn off lights when they’re not in use. Occupancy sensors can serve as a low-cost, easy-to-implement solution. Install them in rooms that aren’t constantly in use, such as bathrooms, maintenance closets, offices, walk-in freezers, and storerooms. If your stores are open all night, you may want to install dual-level switching for overhead lights, allowing you to turn off some fixtures during low-traffic hours.
Turning things down
Some equipment can’t be turned off entirely, but turning it down to minimum levels where possible can save energy.
HVAC temperature setbacks When your store is closed, turn temperature settings down in warming seasons and up in cooling seasons.
Special-use rooms Make sure that HVAC settings in warehouses, stockrooms, offices, and other special-use rooms are at minimum settings.
Cleaning and maintenance
Check the economizer Many air-conditioning systems use a dampered vent called an economizer to draw in cool outside air when it’s available, which reduces the need for mechanically cooled air. If it’s not regularly checked, the linkage on the damper can seize up or break. An economizer that’s stuck in the fully open position can add as much as 50% 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 calibrate the controls; check, clean, and lubricate your economizer’s linkage about once a year; and make repairs if necessary.
Check air-conditioning temperatures With a thermometer, check the temperature of the return air going to your air conditioner. Then check the temperature of the air coming out of the register 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 filters Change air-conditioner filters every month; change them more often if you’re located next to a highway or construction site where the air is much dirtier.
Check cabinet panels and clean condenser and evaporator coils On a quarterly basis, run a maintenance check on your rooftop air-conditioning unit. Make sure that the panels are fully attached, that all of their screws are in place, and that the gaskets are intact so no chilled air leaks out of the cabinet. These leaks can cost $100 per year per rooftop unit in wasted energy. In addition, check condenser coils quarterly and remove any debris that has collected there. At the beginning and end of the cooling season, thoroughly wash the coils. The buildup of dirt and ice on evaporator coils slows down the rate of heat transfer and causes the refrigeration system to use more energy to maintain the same temperature. Cleaning cooling coils regularly helps ensure proper airflow and heat transfer, which can save up to 25% in operational costs and help prevent early compressor failure.
Check for airflow Hold your hand up to air registers to ensure that airflow is adequate. If there’s little airflow or you find dirt and dust at the register, have a technician inspect your unit and ductwork.
Check the refrigerant charge Incorrect refrigerant charge can compromise refrigeration equipment efficiency by 5% to 20% and raise the risk of early component failure. Have a licensed technician check the refrigerant charge of all refrigerated equipment annually.
Check refrigerated cases for air leakage Every month, inspect and replace worn seals and gaskets on the doors and inspect the door closers for proper operation.
Check temperature settings Set refrigerator temperatures between 35° and 38°F and freezer temperatures between –14° and –8°F. Energy is wasted if refrigeration temperature settings drift too low, so check periodically to verify that the appropriate temperature settings are specified.
Add strip curtains to walk-ins Walk-in units can lose a lot of cold air when you open the doors. In one case, simply adding strip curtains to the doors of a 240-square-foot walk-in refrigerator reduced the unit’s energy consumption by 3,730 kWh per year, about 9% of total consumption. Note that, for the best effect, strip curtains must reach the floor to catch the coldest air.
Replace incandescent lightbulbs with screw-in LEDs Replace all incandescent light bulbs that are on for longer than two hours per day with an LED. LEDs are five times more energy efficient than incandescent bulbs and last at least 10 times as long. Also, because they give off less waste heat, they reduce the loads on the store’s cooling equipment. LEDs are a particularly good solution for freezer applications, since their efficiency and lifespan increase in cold conditions.
Install occupancy sensors in walk-ins By replacing light switches with low-temperature occupancy sensors, you’ll reduce lighting energy consumption by about half.
Although the actions described in this section require more-extensive implementation, they can dramatically increase the efficiency of your store. Ask your local utility representative for more information about initiating such projects.
Optimizing refrigeration systems can reduce energy use by 24% relative to standard practice. The following measures yield the largest savings.
Floating head pressure Taking advantage of lower ambient temperatures to reduce refrigerant temperatures is a form of free cooling. One approach is to allow the pressure of the vapor coming out of the compressor (the head pressure) to float (drop with reduced ambient temperatures). This requires an expansion valve capable of operating at lower pressures and flow rates, and such valves are commercially available. In addition, you have to keep refrigerant pressures high enough to avoid flashing (the unwanted vaporization of refrigerant). According to the Washington State University Energy Extension Office, floating head pressure savings generally range from 3% to 10%.
Ambient and mechanical subcooling Reducing the temperature of liquid refrigerant below its condensation temperature is called subcooling. It can be done by either using ambient air or water to remove heat from the liquid refrigerant (ambient subcooling) or using an additional refrigeration system (mechanical subcooling). Colder refrigerant means either more cooling per pound of refrigerant delivered to the display case or shorter compressor run times because less refrigerant is needed, both of which can decrease energy use. Ambient subcooling is often more cost-effective than mechanical subcooling because it requires less equipment.
Evaporative condensers Most condensers in grocery stores are air-cooled, but it’s also possible to use evaporative condensers, which are cooled by water spraying over the condensing coils. Evaporative condensers are more energy efficient than their air-cooled counterparts, but they do have a notable disadvantage: they require a water supply, which often means increased maintenance due to freezing, clogging, and mineral buildup. Evaporative condensers may be cost-effective in dry climates, but the added maintenance may make them unattractive in other climates.
Heat-recovery systems Heat-recovery systems are available that capture waste heat from refrigeration equipment to make hot water that you can use in store. Heat recovered from a 7.5-horsepower compressor can heat all of the hot water a midsize supermarket would use in its kitchens and bathrooms. Often, enough waste heat is also available to supply hot-water coils for space heating in cold weather.
Display-case shields Aluminum display-case shields can reduce refrigeration load from the display case by 8% when applied overnight and by 40% when applied over 24 hours, relative to the load present without the shield. Products are kept colder when the shields are attached and remain colder for several hours after the shields are removed.
Evaporator-fan motors Replacing existing shaded pole motors on evaporator fans with electronically commutated motors will reduce the energy consumption of refrigerator and freezer cases by 60%. Replacing them with Q-Sync motors can reduce energy consumption by up to 75%. Drop-in replacement designs have made this retrofit relatively simple for a technician to perform. Additionally, most evaporator-fan motors in walk-in units run continuously even though full airflow is usually required only about half the time. Consider introducing advanced controllers that slow the fans when full-speed operation is unnecessary. Annual energy savings from adding walk-in cooler controllers can range from 10% to 60%.
Antisweat heater controls The latest antisweat heater controls sense humidity in the store’s ambient air and reduce the operation of their heaters in low-humidity conditions. They promise significant savings and quick payback and are relatively easy to install. Savings can range from 6% to 20%, according to the Washington State Energy Solutions Database.
Smart defrost controllers A smart defrost controller installed in your walk-in freezer monitors several variables and optimizes the number of daily defrost cycles. Depending on the size of the freezer, adding these kits can save hundreds of dollars a year per freezer, compared to conventional defrosting practices.
Automatic doors for walk-in coolers In addition to adding strip curtains to walk-in coolers, automatic doors can provide even greater energy savings, though at a higher cost.
Consider combined heat and power
Combined heat and power (CHP) plants generate electricity at the point of use. They allow the heat that would normally be lost in the power-generation process to be recovered to provide necessary heating and cooling. CHP plants can power your store’s equipment and provide backup power generation when grid power is unavailable, preventing product loss. They can also provide hot water and auxiliary cooling for the facility.
Consider desiccant dehumidification
In humid climates, much of the energy used in air-conditioning goes to removing moisture from the air. Desiccant dehumidification can be a cost-effective solution for removing this moisture because it uses natural gas instead of electricity. In some cases, air-conditioning equipment can be smaller because it only has to cool dry air.
Upgrade to more-efficient lighting
Lighting is critical to creating ambiance and making merchandise attractive to shoppers. High-quality lighting design can reduce energy bills and drive sales. If your facility still uses T12 fluorescent lamps, relamping with high-performance T8 lamps and electronic ballasts can reduce your lighting energy consumption by 35%. Adding specular reflectors and new lenses and reducing the number of lamps can double the savings. Occupancy sensors or timers can add further savings in areas that aren’t always in use, and payback periods of one to three years are common.
LEDs can provide even greater savings. You can replace fluorescent fixtures with LED fixtures, LED retrofit kits, or LED tubes. New fixtures are the most efficient alternative; LED tubes are the easiest, but they may not provide adequate light levels or light distribution.
Because the efficiency of LEDs improves in cold operating environments (unlike linear fluorescent systems where the light output drops in low temperatures), they’re ideal for refrigerated display-case lighting. LEDs are also directional in nature, allowing for less wasted light. As a result, LED case lighting can cut lighting energy use by more than 40% compared to T8 fluorescent lamps.
You can tie LEDs to occupancy sensors so that the cases are only illuminated when shoppers are present. This is a particularly easy savings opportunity for supermarkets that remain open 24 hours a day. When Walmart initiated a pilot LED program integrating occupancy sensors into its LED display lighting, the company estimated the total time lights were on would drop from 24 to 15 hours per day, a 38% reduction. Occupancy sensors aren’t typically used in cases with fluorescent lighting because frequent switching reduces the lamps’ life. However, switching doesn’t affect LEDs. In fact, it lengthens their life—the more time the LEDs spend turned off, the longer the lamps will last.
Using LEDs also reduces case compressor loads. Because the cases can use lower-wattage lamps, there’s less heat to dissipate. Additionally, the heat sink for an LED can be positioned to allow at least some of the heat to dissipate outside the case. With fluorescent lighting, most of the waste heat must be offset with additional cooling inside the case. When LEDs are used with occupancy sensors, they’ll spend less time in the on mode and therefore contribute less to the cooling load. LEDs also provide more-even light distribution, are dimmable, have a long lifetime, and appeal to shoppers at significantly greater rates than linear fluorescent lighting.
Use smart lighting design in parking lots
Reduce light levels Parking lots are often overlit; an average of 1 foot-candle of light (sometimes less) is usually sufficient. Dimming and occupancy-sensing controls can also add to energy savings in parking lots.
Install more-efficient light sources The most common lamps used for outdoor lighting are high-intensity discharge (HID) sources—metal halide and high-pressure sodium (HPS). Fluorescent and induction lamps are also used in parking lots, but LEDs have become the most efficient alternative as their performance has improved and prices have come down.
LEDs can be a good choice for parking lots because the fixtures perform well in the cooler conditions that are typically found outside at night and because LEDs work better with controls than HID products do. LEDs also offer long life (which reduces maintenance costs), provide more-even light distribution, and produce less light pollution and light trespass—properties that improve aesthetics and contribute to energy savings. For example, in recent field testing, the US Department of Energy (DOE) found that LEDs had only somewhat higher efficacy than HPS lamps, but that LEDs provided substantial energy savings thanks to lower overall light levels from better uniformity and less light pollution. The one downside is that you should be wary of the potential for glare.
A parking lot retrofit of LEDs cut lighting energy use by 70% in the DOE-monitored Application Assessment of Bi-Level LED Parking Lot Lighting (PDF) at a Raley’s Supermarket in California.
Consider reflective roof coating Painting the roof of a grocery store with white or other highly reflective paint can reduce the energy required for summer cooling by 25% to 65% and help trim peak demand, as well as increase the life of the roof. Read our cool roofs page to learn more.
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