Electric vehicles (EVs) are becoming increasingly important in supporting the electric grid through frequency regulation services. Recently, new rules related to Vehicle-to-Grid (V2G) technology have been introduced and are now part of the grid codes in many countries. This study aims to determine the most profitable strategy for the operation of EVs, participating in both the day-ahead and frequency regulation markets, taking into consideration the settlement stage for both markets. The models comprise the EV charging demand for a workplace charging station using an individual EV smart charging model that optimizes each EV individually. The EV charging demand and discharging production are used to estimate the bidding capacity for the frequency regulation and spot markets, day-ahead of operation. Subsequently, the settlement stage is considered with actual responses to the grid by utilizing a combination to estimate the imbalances and penalties of forecast error resulting from some individual EV arriving or departing from the office building. In addition, the office building is powered with a PV system. The inputs for the model include mobility patterns and charging sessions for EVs, as well as historical electric market prices and PV power measurements. Various frequency services are investigated, which are primary, secondary, and tertiary. The model evaluates economic profitability in both market German and Swedish markets. A sensitivity analysis exploring changes in prices in the frequency regulation market is conducted. Finally, the findings provide insights into the economic aspects of widespread V2G adoption.