The electricity TSO every two years prepares development plans of the transmission network for a period of ten years, which are evaluated and approved by the Ministry, responsible for energy. The plans take into account the strategic national energy policy; in the planning the prescribed methodology is used that takes into consideration the long-term demand forecast, analysis of expected operational conditions, the level of supply reliability and economic analysis, as well as the possible locations of the new large production sources. Development plans determine the planned physical and financial scope of investments in new facilities on the transmission network. The latest development plans for the Slovenian transmission network were prepared for the period 2015-2024. The electricity TSO in its development plans by 2024 follows the fundamental guidelines covering the construction of an internal 400 kV network loop, new connections with neighbouring systems, management of uncontrolled power flows, and ensuring adequate voltage support and reliable and safe supply in compliance with the recommendations and criteria set by ENTSO-E (European Network of Transmission System Operators for Electricity).

In addition to a development plan, the electricity TSO by 31 January of the year, in which the Energy Agency decides on the regulatory framework, prepares an investment plan and submits it to the Energy Agency. The electricity TSO's investment plan includes a financial evaluation of the investments under the applicable ten-year network development plan to be carried out in the next regulatory period. In the plan, the investments to be funded by the revenue from the congestion-management of cross-border lines under Regulation (EC) No 714/2009 are disclosed separately. In the procedure for setting out the regulatory framework the Energy Agency examines and evaluates the investment plan. The evaluation provides the basis for specifying the planned eligible costs in the next regulatory framework.