## 3 Results  
The required inputs for each scenario (simulation) concerns the hourly demand, the hourly renewables generation, the daily Mean Average Variable Cost (MAVC) of each power plant, the maintenance schedule of each power plant, the daily capacity in each interconnection, the expected hourly price in each interconnected border. The model determines the following outputs: the total hourly energy generation mix per technology type at a daily level (MWh), the hourly system's marginal price at a daily level (\(\upepsilon\)/MWh) and the hourly cross-border electricity flows (net imports or exports) with each interconnected system (MWh).  
As mentioned above, the Greek interconnected power system has been examined. Details on its characteristics are provided in recent papers [13; 14; 15; 16]. In Greece, the Public Power Corporation (PPC) has a dominant position with about 80% of the retail market at the end of the year 2018. Moreover, it has a diversified portfolio of power plants, including lignite-fired, combined cycle natural gas units, and big hydro units, as well as a relatively limited share in renewables capacity. The installed capacity, as well as the mix of units, compares to the independent power producers, who own only natural gas units and renewables, not operating currently any lignite or big hydro unit. However, three lignite units are expected to be purchased by IPPs within 2019, which is the situation in the examined case. This role of PPC enables the adoption of a strategy that could affect wholesale prices and mix. This was examined in a recent paper [15] concerning the adoption of a new market algorithm. The consideration of bilateral contracts as a tool for potentially influencing the wholesale market is the main focus of this paper.  
The model provides several outputs, from which the most important are the hourly energy generation mix per technology type at a daily level (MWh) and the hourly system's marginal price at a daily level (\(\upepsilon\)/MWh).  
Several scenarios have been examined. More specifically, 24 typical days (two per month) have been examined to examine four scenarios per typical day, which examine the evolution of bilateral contracts in the retail market share of PPC, taking values 10%, 15%, 20%, and 25% of the load PPC represents. Therefore, 96 scenarios have been formed. The excessive number of scenarios do not allowfor the provision of results for all scenarios. Indicative scenarios are presented that have been chosen to enable the provision of interesting and robust concluding remarks.  
The weighted average annual System Marginal price for different share level of the bilateral contracts is almost identical in the examined cases, as it is estimated to be 63.11, 63.12, 63.16, 63.12, and 63.06 \(\upepsilon\)/MWh for 0%, 10%, 15%, 20%, and 25%, respectively. Figure 2 provides the average daily System Marginal price for the different typical days and the different share level of the bilateral contracts, which again depicts that results are identical for the typical days in all months.  
Figure 3 provides the annual production (in TWh) per Producer and Fuel type, for different share level of the bilateral contracts (10%, 15%, 20%, and 25%). Figure 4 provides the evolution of wholesale price for different scenarios (units that participate in the bilateral contracts), different dates, and different level of bilateral contracts (10%, 15%, 20%, and 25%). The different scenarios concern a different number of thermal units from the PPC that participate in the bilateral contracts, i.e., BLOCKS_5 LIG, BLOCKS_5 LIG_3 NG mean that five lignite or five lignite and three natural gas units participate, while the remaining capacity is bid with block orders types. On the contrary HOURLY, concern participation in the energy exchange with hourly orders. The impact of hourly and block order types has been thoroughly examined in the recent paper [15].  
Figure 4: _Cont_.  
Figure 3: Annual production (in TWh) per Producer and Fuel type, for different share level of the bilateral contracts.