Increased energy consumption in industrial and commercial subtransmission networks has considerably increased the loading of transmission lines. In order to satisfy consumer demand, this capacity should be increased. Three main ways of increasing capacity are using high-temperature low-sag (HTLS) conductors, increasing the number of bundles, and building new subtransmission lines. This paper is a report on an attempt to increase the power transfer capacity of Tehran Regional Electric Company (TREC) subtransmission network through the above-said methods. For the purpose of re-conductoring, the existing LYNX conductors (ACSR) in the network under study were replaced with equivalent HTLS conductors (ACSS). Calculations were performed for sag tension, current carrying capacity, and electrical parameters. The methods were simulated using DigSilent software for the peak load in the year 2014. The three methods were compared in order to determine which one produces the best results. The comparison took account of the costs associated with power loss and considered technical and economic issues.