Economics of LED Lighting

Lighting technologies have improved significantly over the past 10 years and now provide multiple options for supplemental plant growth lighting in greenhouses and sole-source lighting for indoor production. In 2014, the most efficient light emitting diode (LED) and high pressure sodium (HPS) fixtures had nearly identical efficiencies at 1.66–1.70 µmol per joule, but the initial capital cost of LED fixtures per photon delivered was five to ten times more than HPS fixtures. This high capital cost meant that the cost per mole of photons was thus 2.3 times higher for LED fixtures than for 1000-W HPS fixtures, calculated over a five-year period for electricity and fixture cost. The long-term maintenance costs for both LED and HPS technologies are small, and similar, so the economic incentive for using LEDs was only realized when a user took advantage of their more focused photon distribution pattern. Since 2014, the photon efficiency of LED fixtures has increased and the most efficient LED fixtures now exceed the best HPS technology (1000 W, double-ended). The cost per photon of LED fixtures for plant growth lighting is still high, but payback periods, compared to 1000 W HPS, of 8–20 years can be achieved in applications that utilize the lights for more than 4000 h a year. The payback period can be more rapid if users can take advantage of the focused output of LED fixtures to increase radiation capture. The lowest lighting system costs are achieved when an efficient fixture is coupled with effective canopy photon capture. We are continuing to evaluate advances in technology as they become available.

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