In MN, “daylight harvesting” must be provided for fixtures within 15’ of a window, this can be automatically done by a photocell connected to a dimming relay, o

In MN, “daylight harvesting” must be provided for fixtures within 15’ of a window, this can be automatically done by a photocell connected to a dimming relay, or manually with a dimmer switch. Offices with windows must also have controls, either photocell or manual-on/auto-off (vacancy sensor). Interior enclosed spaces are allowed to have standard single-pole switches, but these days we’re putting in occupancy sensor switches, the tenants prefer them. Many or most of the installs have occupancy sensors for general lighting, or a time clock that shuts them off during non-business hours. A 32w LED 2x4 is roughly equivalent to a 96w 3-lamp CFL 2x4, or 3x as efficient. You can power roughly 135-140 32w fixtures on a 277v 20A circuit [(277x20x.8)/32] which will illuminate ~11k sq ft. With 2 20A circuits, you can light up an entire office tower floor (floorplates are generally 18-23k sq ft). Assuming a ~10,000 watt load, and $0.08/kWH, it costs $0.80/hr to illuminate 20,000 square feet. It’s not as big of an energy waste these days, but it’s still a waste.