To reduce power loss in a transformer, designers and operators focus on both core and copper losses. Design measures include using high grade silicon steel or amorphous cores, optimizing flux density, and selecting appropriate conductor sizes to limit I²R losses. Good cooling systems keep temperatures low, reducing resistive losses and insulation aging. In operation, maintaining near optimal loading, corrective power factor compensation and avoiding over excitation also help. Utilities sometimes replace older transformers with higher efficiency units to cut long term no load and load losses in the network.