An on-site energy management system, EMS, for an energy autonomous cell site in a cellular network wherein the cell site comprises at least one energy supply unit, at least one energy storage unit, and as at least one consumer at least one radio transceiver unit, wherein the EMS comprises at least: - a decision logic module with data acquisition means and data processing means wherein the decision logic module is implemented on a computing device that can be integrated in the cell site or is at least operably coupled to the cell site, wherein the decision logic module is configured to be iteratively executed at a given time interval wherein in each iteration the decision logic module is configured to initiate and initiates at the cell site in parallel controlling energy distribution, energy storage and energy reduction, by acquiring, using the data acquisition means, at least data about current energy generation and consumption at the cell site, current energy storage capacity at the cell site and current energy reduction commands for the cell site and providing, using the data processing means, respective energy distribution control data, energy storage control data and energy reduction control data, - an interface module that is implemented on the computing device that can be integrated in or is at least operably coupled to the cell site wherein the interface module is configured to detect the respective control data and to initiate, depending on the control data, altering an operating condition of/at the cell site and/or providing a status information about the cell site in response to the control data, wherein controlling the energy storage comprises constantly monitoring, by the EMS, and analysing, by an energy storage management logic as a component of the decision logic module of the EMS, the current storage capacity on the cell site, calculating, by the energy storage management logic, a worst-case discharge time, t_crit, where the energy storage unit is estimated to be completely discharged, retrieving a service time from site specific settings, the service time being the time that is needed to refill the energy storage unit by an emergency service, comparing the worst-case discharge time with the service time and if the worst-case discharge time is smaller or equal to the service time, sending, by the energy storage management logic, an emergency notification and requesting, by the energy storage management logic, the emergency service to refill the energy storage unit. - a decision logic module with data acquisition means and data processing means wherein the decision logic module is implemented on a computing device that can be integrated in the cell site or is at least operably coupled to the cell site, wherein the decision logic module is configured to be iteratively executed at a given time interval wherein in each iteration the decision logic module is configured to initiate and initiates at the cell site in parallel controlling energy distribution, energy storage and energy reduction, by acquiring, using the data acquisition means, at least data about current energy generation and consumption at the cell site, current energy storage capacity at the cell site and current energy reduction commands for the cell site and providing, using the data processing means, respective energy distribution control data, energy storage control data and energy reduction control data, wherein the decision logic module is implemented on a computing device that can be integrated in the cell site or is at least operably coupled to the cell site, wherein the decision logic module is configured to be iteratively executed at a given time interval wherein in each iteration the decision logic module is configured to initiate and initiates at the cell site in parallel controlling energy distribution, energy storage and energy reduction, by acquiring, using the data acquisition means, at least data about current energy generation and consumption at the cell site, current energy storage capacity at the cell site and current energy reduction commands for the cell site and providing, using the data processing means, respective energy distribution control data, energy storage control data and energy reduction control data, - an interface module that is implemented on the computing device that can be integrated in or is at least operably coupled to the cell site wherein the interface module is configured to detect the respective control data and to initiate, depending on the control data, altering an operating condition of/at the cell site and/or providing a status information about the cell site in response to the control data,