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Case Study: Detroit Lakes Street Department Maintenance Building

Lighting retrofit saves energy in city’s vehicle storage garage

Objectives. The lights in many vehicle storage garages throughout the state are left on most of the time—wasting energy. Until 2010, this had been the case at the 4,700 square-foot Detroit Lakes Street Department Maintenance Building. That’s when the city implemented a major lighting retrofit to save energy for its vehicle storage facility.

Implementation. The City of Detroit Lakes installed motion detectors to control the lights and replaced the old T12 lamps and electronic ballasts with modern efficient fixtures and lamps. Several 400-watt metal halide high-intensity discharge (HID) lamps were replaced with high bay fluorescent fixtures.

Outcomes—energy saved, lighting improved. The savings have been dramatic—about a 25 percent reduction in kWh consumption. “The savings have more to do with the motion detectors than the light replacements,” says Brad Green, street department supervisor. “Because much of the snow plowing is done at night, workers would leave the building and not turn off the lights. Many times, before the sensors were installed, the lights would be on 24 hours a day. Now our lights are turned off when people are not in the building.”

Monthly Electric Cost Graph

Documenting results. The chart above, from the Minnesota B3 Benchmarking database, shows the Street Department Building’s actual electrical use on the blue bars, and what the predicted consumption would likely have been without the lighting improvement on the dashed line. The dashed line is a projection of the 2010 (pre-project) energy use that has been normalized to account for weather variations. The savings, compared to the 2010 base year, were 23 percent in 2011 and 24 percent in 2012.

The lighting retrofit has provided additional benefits, including a better work environment, adds Green. Gone is the annoying glare of the old HIDs, and with the new high bay fluorescents, there’s no waiting for the lights to achieve full brightness.

Value of B3 Benchmarking tool. The Minnesota B3 Benchmarking tool is available for all state, local government, and public school buildings. It allows users to track their buildings’ energy use, monitor the performance of energy improvements, and allow building portfolio managers to readily identify poor energy performance. Josh Mason is the energy services specialist at Detroit Lakes Public Utilities who maintains the B3 database for Detroit Lakes city buildings. With the city serving as the distribution utility, Mason says it is easy for him to retrieve the electric consumption data. 

The B3 tool is provided by the Minnesota Department of Administration and the Minnesota Department of Commerce, with funding from all utilities in the state supporting the effort. To add your building, go to the B3 website and click on “Contact Us.” 

Funding. The majority of the project cost was covered by a grant from the Minnesota Department of Commerce and U.S. Department of Energy. The grant was provided by the American Recovery and Reinvestment Act of 2009, federal stimulus funding designed to save energy and create jobs. A rebate from Missouri River Energy Services covered most of the remaining costs. Detroit Lakes Public Utilities gets its electricity from Missouri River Energy Services, and that supplier provides a program called Bright Energy Solutions that offers rebates for efficient lighting projects. With the national phase out of magnetic ballasts and T12 lamps, some Minnesota utilities still offer limited rebates for converting such lighting systems, but replacement of older HID lights and motion detectors is usually covered. 

Resources for local government projects. As Detroit Lakes has demonstrated, cities and other public entities can work with their local gas or electric utility when seeking energy improvements. Utilities can help with building assessments and may provide rebates for energy efficiency improvements.

The Minnesota Department of Commerce, Division of Energy Resources (DER) provides technical support to local government units, state agencies, school districts, and institutions of higher learning that are seeking energy efficiency and renewable energy measures. Contact DER at to discuss which of its energy efficiency programs can be of help.

The U.S. Department of Energy’s Building Technologies Office also provides helpful resources for building retrofits.