Energy costs in grocery stores can be quite high. But thanks to an energy audit performed by the Montana Resource Efficiency Program (MREP), an organic grocery in Helena has a variety of options to reduce those costs.

The Real Food Store is an organic grocery and deli, located in Helena, Montana. The one-story retail facility has an open floor plan that includes a group of offices, a break room, and a meeting room. The building consumes electricity and natural gas at a higher rate in summer months, as shown in Figures 1 and 2. This indicates that cooling is the largest energy consumption source.

HVAC Recommendations

The Real Food Store building’s HVAC systems consists of five rooftop units, or RTUs, each designed for different areas of the store. These rooftop units use natural gas to heat and electricity to cool with the condensers integrated into each unit. The ductwork is exposed and not insulated, and the addition of insulation could increase efficiency. Insulating the east and north perimeters of the crawlspace walls could also negate heat loss in winter months.

There are several employee comfort issues in the office area of the store, which is very cold in winter months. This problem can be contributed to a bad thermostat location or improper zoning for the thermostat. It could also be the result of incorrect venting, the need for weatherization of windows in the office areas, or a large return grille that is located directly across from the offices. MREP strongly recommended a retro-commissioning study to determine the source of uneven heating and cooling in this area.

The older rooftop cooling units do not have energy-saving options, such as variable frequency drives (VFDs) or electronically communicated motors (ECMs).  The store can retrofit the units with VFDs and ECMs to allow the efficient motors to work at speeds associated with demand.

Refrigeration is the largest cost for most grocery stores. There are a couple options that can help diminish the cost and energy use of the store’s refrigeration system. These options are expensive to implement and are recommended only if a complete overhaul of the system is necessary in the future. If a new design is required for the condensers, we recommend constructing a racking system for the condensers. This would combine the condensers into one control room and run them in parallel to maximize the energy efficiency.

Hot-water heat recovery is another energy-efficiency measure to consider. Grocery stores have a great opportunity to use the heat rejected by the condensers for domestic hot water heating. Hot-water heat recovery requires additional plumbing and equipment but can save a large amount of energy by preheating the incoming water before reaching the hot water heater and can save 300 therms of natural gas a month. This energy-saving measure could be implemented without an overhaul of the refrigeration system.

Domestic Hot Water Heating Energy Recommendations

According to the deli manager, the Real Food Store serves on average 170 hot meals per day and 170 cold meals per day. It is estimated that the store’s deli uses 2,890 gallons of hot water per day[1]. This adds up to approximately 500 therms of natural gas a month, costing upwards of $375 per month for hot water heating alone. Below are some recommendations for reducing this cost:

• Install low-flow kitchen and bathroom faucets
• If the dishwasher, ice machine, or steam cooker needs replacing, invest in an ENERGY STAR-certified model
• Install high-efficiency pre-rinse spray valves for dishwashing

[1] ASHRAE (2011). Hot-Water Requirements and Storage Equipment Sizing. ASHRAE Handbook: HVAC Applications (pp.50.11-50.13). Atlanta, GA: ASHRAE.

Lighting Recommendations

The store’s lighting consists of metal halides, fluorescent tubes, CFL, incandescent, and PAR 30 bulbs. MREP engineers developed an LED conversion design with the following savings and payback:

• LED Cost: $8,567
• Utility Incentive: $2,120
• Net Cost: $6,447
• Annual Bill Savings: $3,570
• Annual Energy Savings: 24,930 KWH
• Simple Payback with Energy Savings: 1.8 years

Following a lighting audit and recommendations made by the Montana Resource Efficiency Program (MREP), the Livingston (Montana) School District is poised to save over $36,000 in lighting costs each year.

The School District is comprised of five schools, which collectively serve a student body of some 1,400 students from late August until late May each year. In addition, the district maintains a bus barn.

Based on recommendations from MREP, the school district is currently converting its lighting to LED.  The lighting throughout the District was primarily fluorescent T8 fixtures with the exception of the high school, which was retrofitted with 28-watt T5 fluorescents in 2011 when it was remodeled. Lighting accounted for nearly 25% of the districts electric consumption. Total electric usage for the district is shown in the table below.

The estimated cost to upgrade lighting in the schools was $30,750 after utility rebates were applied.  Annual energy cost savings is estimated at $36,692, for a simple payback of just over 10 months. This payback can be shortened further by rising utility rates and increased longevity of the LED bulbs.

Considering the cost of the short payback, this project was a sound investment for the District. Costs, savings, rebates, and payback are detailed below.

The Granite County courthouse, located in Philipsburg, Montana, was constructed in 1913 of brick and Montana granite. The building is three stories tall and is comprised of heavy woodwork, large wood and granite columns, a large dome with a stained glass skylight, and tile mosaic floors.

The courthouse recently completed a large lighting project, which included the replacement of old light fixtures with new energy-efficient LED fixtures. The 140 fixtures changed during the project qualified for $7,000 in utility rebates from a lighting rebate program and will result in $4,928 per year in energy bill savings. The net cost of the project was $29,835, giving the project a simple payback of about six years. Here is a quick summary of the project:

• Annual bill savings: $4,928
• Project cost: $36,835
• Rebate: $7,000
• Net cost: $29,835
• kWh savings: 64,056
• Simple payback: 6.05 years

Enterprise Holdings now has some specific energy-efficiency options that could improve its bottom line, thanks to a comprehensive energy audit of its facilities performed by MREP.

Enterprise owns seven rental facilities throughout Montana, each comprised of office space and a washing garage, as well as one main office in Helena. MREP experts visited all eight facilities to assist in identifying cost-effective efficiency measures for each building. The recommended measures include installing programmable thermostats for office spaces, insulating gaps in exterior doors, especially under garage doors, and upgrading lighting to LED.

PROGRAMMABLE THERMOSTATS

Programmable thermostats are simple to install and inexpensive, yet they can result in significant energy cost savings by reducing the set temperature during times when offices are closed, such as evenings and weekends. Five of Enterprise’s eight offices are recommend to install these thermostats.

• Annual energy savings: 1,180 therms
• Annual cost savings: $720
• Projected cost: $160
• Simple payback with energy savings: 0.22 years

DOOR INSULATION

A number of exterior doors have gaps present, allowing air to flow into the space and negate the heating or cooling from the HVAC systems. Fortunately, there is a simple solution: applying stick-on foam to doors to fill the gaps and help maintain comfort levels in interior spaces. Reducing drafts can also decrease the use of space heaters among office employees, further increasing energy savings.

Garage doors in car-washing areas had large gaps between the doors and concrete floors. The thermal image on the right shows the gap at the bottom of the garage door as it lets cold air in. Adding insulation here will help reduce the need for space heaters and save on natural gas costs.

Weatherstripping is a very inexpensive and cost-effective way to prevent the escape of heating or cooled air. This measure can also be applied to windows and window sills.

LED LIGHTING

Many of Enterprise’s offices and garages had fluorescent T8 tube lighting, and upgrading these to LED will save a significant amount of energy. MREP’s lighting analysis resulted in the following costs and savings:

• LED replacement cost: $8,332
• Utility incentives: $3,416
• Net cost: $4,917
• Annual energy savings: 43,344 KWH
• Annual cost savings: $5,285
• Simple payback with energy savings: 0.93 years

SOLAR PV SYSTEM

Enterprise Holdings also expressed interest in a solar photovoltaic (PV) system for its Helena and Great Falls facilities. MREP analyzed roof- and ground-mounted systems for the Helena facility and found that a roof-mounted system would be limited to 10.4 kW, which would produce 18% of the building’s electricity usage. A ground-mounted system would allow the maximum size of 50 kW and produce 76% of the building’s electricity usage. The Great Falls facility could accommodate a 10-kW roof-mounted system that would produce about 60% of the facility’s usage.

Currently, there is a 30% tax credit of the cost of the system to any tax paying business. MREP recommended that Enterprise take advantage of this credit while it is still in place as it is set to phase out starting in 2020.