In this study, the economic benefits of using a probabilistic-dynamic approach (PDA) in the quantification of operating reserves are investigated and compared with more traditional quantification rules in power systems with high penetration levels of wind power. To do this, a comprehensive methodology to quantify different operating reserves categories within the real-time system operation is proposed. The quantification is based on an iterative process where the total costs of the system are minimised, that is the sum of the operating costs (including the additional costs of partially loading generating units due to operating reserves) and the costs of the expected energy not supplied. The PDA considers conventional generation outages; load and wind forecast uncertainty on an hourly basis as well as load and wind variability in a 10 min time frame. The authors use the Chilean power system to demonstrate the efficiency and advantages of the proposed reserve quantification approach.