Coalition talks have produced a blueprint for the target, aiming for more annual carbon emissions savings than its current renewables quota of roughly a third, as it weans itself away from traditional energy sources.
“This means more renewables capacity must be integrated and transported,” he said in an interview on Wednesday.
“The rapid expansion of grids creates bottlenecks, it makes networks less stable and costs consumers money,” he added.
TenneT’s German unit, accounting for the bulk of its business and active in the German region with the highest renewable share of energy, reported grid management costs of 984 million euros ($1.22 billion) for 2017 – a vast increase from 660 million euros in 2016.
“These sums will not go down in the next few years,” Hartman said.
Depending on weather patterns, the company’s job is to curtail or add power capacity to grids to keep supply stable.
Grid costs are shared by consumers as part of their final bills, making up a quarter of their total costs.
Crucial new north-south power lines, aimed at relieving transport bottlenecks, pursued by TenneT, SuedLink and SuedOstLink, are unlikely to materialise before the middle of the next decade.
Their construction has failed to keep pace with the strategy of bumping up green power capacity to replace nuclear energy and fossil fuels, largely because they must be put underground to quell opposition.
Hartman said his company was focusing for now on digital business models to improve the efficiency of grids.
These include sharing wind feed-in data with northern German power network Arge and utility Statkraft, and with solar equipment maker SMA and Volkswagen, to better align grid usage.
“We get to see likely production data and thus improve our forecasts,” Hartman said, allowing TenneT to minimise grid management costs. ($1 = 0.8071 euros)