Anthropogenic processes have led to high levels of reactive nitrogen entering freshwater ecosystems. This increase in reactive nitrogen levels has caused several adverse environmental and health effects and has resulted in higher deposition rates of nitrates to freshwater ecosystems. The costs and benefits associated with nitrate deposition have been analysed by the European Nitrogen Assessment (ENA) for European countries. However, no studies similar to this have been done for the South African context. The aim of the study was to present a cost analysis of nitrate deposition originating from power station NOx emissions. The objectives were: to examine the changes in nitrate deposition for the years 1980, 2005, 2006 and 2014; to determine the costs associated with nitrate deposition to freshwater ecosystems for the South African context; to calculate the costs of power station emissions to the Vaal River; to consider how European costs differ from South African costs; to consider the impact of the NEMAQA of 2004 and finally, to evaluate the likelihood of these costs being incurred. The years that were selected for this study were chosen due to availability of data, which were supplied by EScience Associates. Three scenarios were considered for each of these years: Scenario 1 was a case in which Eskom operated as usual without any retrofits of power stations, Scenario 2 considered the implementation of the Eskom air quality management strategy and Scenario 3 considered full compliance with the minimum emissions standards set out in the NEMAQA of 2004. The costing method followed the ENA approach, whilst considering the South African context by consulting the relevant literature. The monetized annual costs for the South African context were: mitigation options for improving water quality; increased coal consumption due to power station interventions; agricultural costs; water purification and waste treatment; health impacts and loss of biodiversity as a result of acidification and eutrophication. Power station interventions were found to be the only capital expenditure. The nitrate deposition per unit of electricity generated was expected to decrease, due to changes within the electricity mix of Eskom during this period. Furthermore, the least costly option was expected to be a scenario in which no intervention was made by Eskom to reduce emissions, due to the high capital cost associated with retrofitting low NOx burners in the older power stations. The final expected outcome was that the National Environment Management: Air Quality Act (NEMAQA) of 2004 would have led to a significant decrease in the emissions and, therefore, nitrate deposition to the Vaal River. The costs that were calculated for the South African context differed greatly from the costs in the ENA, indicating that the European costs could not be used directly for the South African context. Furthermore, the results showed that the costs of nitrate deposition increased between 1980 and 2005, decreased between 2005 and 2006 and increased again between 2006 and 2014. Between 1980, 2005 and 2006, a clear link is seen between electricity generated and nitrate deposition. Even though electricity generation increased from 2006 to 2014, the 2014 emissions data show that emissions decreased over the same period. The cost of a fine for non-compliance to emission limits is R10 million. The lowest cost calculated for each year and scenario was found to be Scenario 1 for 1980, and was approximately R 70 million of costs arising from nitrate deposition from power station emissions. The R 70 million, therefore, does not include mitigation options for water quality, increased coal consumption and power station interventions. Therefore, the fines associated with non-compliance, which occur in Scenario 1 and Scenario 2, should be increased to force compliance. The total cost associated with Eskom’s air quality strategy, calculated as part of scenario two, was the lowest cost option for 1980, 2006 and 2014. In 2005, the lowest cost option was scenario 1, where no retrofits were done by Eskom. This indicated that there was a trade-off between capital expenditure for low NOx burners and the annual costs, listed previously. This study concluded that when air quality policies, such as the NEMAQA of 2004 are implemented without stringent enforcement, the desired result is not achieved. The findings in this study show that no significant decrease in nitrate deposition occurred between 2005, when the NEMAQA of 2004 was released, and 2014, which was almost 10 years after the policy was implemented. This study makes a valuable contribution to informing policy makers on the impact of reactive nitrogen addition to the environment. Future research should be done on the cost of agricultural nitrate deposition to the Vaal River, considering that these inputs to the Vaal River are several times larger than those of deposition from power station emissions and could, therefore, have costs of a larger scale associated with them.