The services provided by HEP-OPS to system users and other market participants are divided into:
- electricity transmission services
- transmission within the Croatian power system,
- cross-border transmission,
- system services
- system operation,
- frequency control
- voltage control
- congestion management,
- system restoration after disturbance,
- production of part of reactive energy
HEP-OPS provides the services using its own resources and capacities and by procuring the services on the market from providers of these services. HEP-OPS negotiates with service providers the conditions for the provision of ancillary services. In the process of system operating the HEP-OPS determines, exercising the care of a good manager, which, how much, by whom and when ancillary services are to be provided, taking into account market principles and technical criteria of security and reliability of the power system.
The services are attributable if the provider or user of a particular ancillary or system service in the known scope can be identified, which is used as basis for the calculation of charges and costs. The users of attributable services bear their own costs and HEP-OPS ensures that the providers of attributable services receive compensation according to contractual prices of services. Non-attributable services are services which users are not recognizable. The costs of non-attributable services are borne by all network users and these costs are included in the charge for transmission network use.