Abstract The construction of high-voltage overhead transmission lines on farmland implies a permanent easement, involving expropriation of land and depreciation of the remaining farm area. The Italian system operator should pay compensation for both aspects, but recognizes only the former. Therefore, landowners often appeal to the law courts and claim compensation for the depreciation of the entire non-occupied area, often obliging the system operator to pay substantial amounts. This delays the provision of new power lines and increases their respective costs. In order to verify the correctness of the modus operandi by the system operator and landowners, a study was carried out into the impact of several characteristics of power lines on farmland value in northern Apulia, south Italy. The results highlighted that the area occupied by plinths and cabins, the height of towers and the type of intersection were the main sources of depreciation, which varies depending on the crop. Moreover, depreciation on the residual area exists, but only involves two narrow strips of land on either side of infrastructure. Finally, it is not constant, but tends to decrease rapidly as the distance from the infrastructure increases, and zeroes at 30–70 m from the power line.