The main systems that consume energy in industry include HVAC, compressed air, heating and cooling processes, electrical systems, lighting, motors, boilers, refrigeration, drying, and waste treatment. Approaches to improving energy efficiency include passive measures like using more efficient lighting and motors, which can save 10-15% of energy without human involvement. Redesigning an entire industrial power loop to use bigger pipes and smaller pumps, as well as laying pipes before adding equipment, can reduce power usage by up to 92%.