From this story:
"For five days last week in a parking lot in downtown Vancouver, this billboard was lit around the clock by pedal power to demonstrate the energy efficiency of LED lights. The DDB/Vancouver project, on behalf of BC Hydro, required some 120 volunteers — from the client, the agency and local organizations — to keep the 1,500 LED lights aglow. According to BC Hydro, if the billboard featured traditional mini incandescent bulbs, only 120 lights could be lit with the same amount of energy."Via.