Parallel operation of the transformer in context of energy conservation: The transformers operate near their maximum efficiency around 70 % to 100 % of their rated loads. For huge establishments drawing highly varying powers at different times supplying from single transformer will be uneconomical and inefficient as the efficiency varies. Because at light loads, a higher rated transformer has higher constant losses compared to a lower rated one. Also the allied systems for the transformers draw power thus reducing the overall efficiency. Hence to operate the system at highest efficiencies as much as possible, parallel connected transformers are utilized such that at lower power requirements one of those with lower capacity (and hence lower power losses) in parallel will supply at around its maximum efficiency while the other is switched off thus saving its low load losses. This is done as per the requirements of the loads.