Also, nuclear power plants are likely to be the largest generating units in the electrical system, and thus increase the amount of spinning reserves needed to ensure grid stability. Their high load may also require upgrading the grid connection to at least 300 kV, and up to 400 kV for a new European pressurised reactor (EPR). Finally, the necessity of locating nuclear plants close to water sources for cooling purposes may require additional investments in the extension of the existing grid.