ROSSLYN, Va.—The National Electrical Manufacturers Association (NEMA) published NEMA LSD 79-2018 Predicted Energy Savings from Lighting Systems, a new white paper that includes a framework used to gauge the effectiveness of different lighting control methods.
“While the potential to save energy short term is very clear, a method is necessary to determine the long-term average savings that can be captured based on the specific efficiency measures selected by a building owner,” said Dr. Robert Nachtrieb, Lead Scientist, Lutron Electronics Company, and chair of the LSD 79 ad hoc committee. “This paper describes the complexity of this determination and suggests a potential path forward.”
NEMA LSD 79-2018 is available as an electronic download at no cost on the NEMA website.
Tagged with NEMA
Although this white paper is quite good, there are some concerns. At least in retrofits, there does not need to be HE trim, because maximum lighting can be brought down to that level, and so can daylighting. In ‘owned’ spaces like private offices and elementary school classrooms, annual hours of operation can often increase with occupancy sensors, because people, who used to manually turn off lighting when they left usually allow for the 10 – 15 minute automatic delay from the sensors. Table 1 would be better if it compared the same LEDs with and without dimmer and occupancy sensor. Modified internal rate of return (MIRR) is better than internal rate of return (IRR). Often 0.25 WSF or less can be attained with good LED lighting in offices, classrooms, etc. Let’s look at a 160 SF private private office with 2 20W 140 LPW LED troffers or troffer kits. Annual electrical use would be $15.00 based on $0.125/KWH, which is near the national average, at 3000 annual hours, controlled by a time clock with the worker never turning lights off manually. Based on California Energy Commission’s (CEC) Database for Energy Efficiency Resources (DEER) numbers, an occupancy sensor reduces time by 16%, which would only save $2.40 per year. Parts and labor for a wall mounted sensor may be $65, which would be a 27 year payback, which is probably an infinite payback, because the sensor will probably not last that long. Even if the sensor reduces operating hours by 50%, payback is still 8.7 years, which is unacceptable to most end customers. With high performance LED systems, lobbyists and energy codes should stop mandating controls at least for retrofits. Let the free market decide, based on energy benefits and non-energy benefits.