Electrical power generated at power plants must be transmitted to its ultimate users. This process requires transmission lines to carry the heavy power loads over long distances. These transmission lines perform the heavy duty work and require stronger supports and larger wires. There are several advantages to placing the transmission lines overhead as opposed to underground.
When deciding whether to put transmission lines overhead or underground, installation costs become a primary concern for power companies. The advantage in initial capital costs goes to overhead lines. Cost becomes a primary concern of power companies when determining how to construct transmission lines. According to Florida Power & Light Company (FPL), it costs five to 15 times more to install transmission lines underground, making it prohibitive and rarely used except in densely populated urban areas where overhead is not feasible.
Underground power lines are more costly to repair. In addition, it generally takes longer to repair than overhead lines due to the difficulty in reaching the underground problem. Delays in repairs create many problems, including power outages, and with transmission lines, a cascading effect due to the many customers served by one set of transmission lines. Maintenance costs have to be calculated along with the initial capital installation expenses when determining whether or not to go underground so the advantage on repair costs goes to the overhead transmission lines.
While overhead transmission lines may be considered unsightly, they do not impact the environment in the manner underground lines would when crossing large expanses of land. Electrical lines pass over wetlands and fragile ecosystems and it becomes easier to avoid injury to those areas when the lines are overhead as opposed to digging up trenches to bury electrical lines.