During realization of bilateral supply contracts and electricity trade contracts deviations between realized and scheduled values are present. Since the power system operation is based on the balance between the electricity demand and supply, there is a constant need for system balancing. The real time system balancing is responsibility of Croatian Transmission System Operator (CTSO).

HROTE calculates the balancing energy and CTSO, according to the calculation, charges balancing costs from balance responsible parties. According to the new model of the electricity market in Croatia, all market participants must be a members of some / one balance group, whose leader is responsible for the deviations of whole balance group.

Balancing energy calculation and invoicing are carried out in accordance with the Electricity Balancing Rules, calculation of unit prices for Balancing energy is carried out in accordance with the Methodology for determining the price for the settlement of balancing energy.

According to Article 6, paragraph 2 of the Methodology for determining the price for the calculation of balancing energy (Official Gazette, Nos. 71/16, 112/16) HROTE is obliged to publish a correction coefficient Δj.


Δj for months in 2019:

Value of  correction coefficient Δj:
2019	January	February	March	April	May	June	July	August	September	October	November	December
Δj	0,206	0,117	0,162	0,316	0,366	0,315	0,268	0,246	0,286	0,400	0,212	0,287

 
Δj for months in 2018:
 

Value of  correction coefficient Δj:
2018	January	February	March	April	May	June	July	August	September	October	November	December
Δj	0,1	0,112	0,1	0,1	0,122	0,1	0,135	0,1	0,198	0,163	0,1	0,1

Δj for months in 2017:
 

Value of  correction coefficient Δj:
2017	January	February	March	April	May	June	July	August	September	October	November	December
Δj	0,1	0,4	0,4	0,1	0,228	0,146	0,145	0,217	0,100	0,212	0,194	0,194

 
Balancing group imbalances in first (monthly) imbalance settlement are calculated for each settlement interval (hour) and represent a difference between the balancing group’s realisation and balancing group’s market position according to the formula below (Balancing energy calculation unit is 0,001 MWh):
 

Market position of a balancing group is the difference between contracted sales (including exports) and contracted purchase (including imports) of electricity on a wholesale market and difference between sales and purchase of balancing and other ancillary services energy of all balancing group members in a settlement interval (hour). It is calculated according to the formula below:
 

Realisation of a balancing group member is a difference between total electricity delivered into the system and total electricity taken over from the system by the individual balancing group member in one settlement interval (hour) and shall be calculated according to the formula below:
 

Balancing energy prices

If the imbalance of the balance group is positive (Realisation – Market position > 0)	Unit price for the imbalance settlement according to which HOPS pays to the balance groups is Cp
If the imbalance of the balance group is negative (Realisation – Market position < 0)	Unit price for the imbalance settlement according to which balance grop pays to HOPS is Cn

 
Croatian Transmission System Operator will procure balancing energy and issue monthly invoices for imbalances of balancing groups based on the calculation of imbalances conducted by the Electricity Market Operator. If a balance group has negative imbalance for the first (monthly) imbalance settlement then Transmission System Operator issues invoice to the Balance group (BRP). If a balance group has positive imbalance for the first (monthly) imbalance settlement then Balance group (BRP) issues invoice to the Croatian Transmission System Operator. In the second (annual) imbalance settlement the difference between metered realisation pursuant to the General conditions for system use and electricity supply and realisation in the first (monthly) imbalance settlement pursuant to the Rules for application of standard load profiles shall be calculated.
Settlement interval in the second (annual) imbalance settlement is a calendar month, and the settlement period is a calendar year.
Imbalances of individual balancing groups in the second (annual) calculation of imbalances is calculated by the Electricity Market Operator by the 10^th September at the latest in the year following the settlement period (calendar year), based on realisation data of balancing group members and data on actual losses in the distribution system delivered by the Distribution System Operator.
Balancing group imbalance in the second (annual) imbalance settlement is a sum of imbalances of all metering points belonging to the balancing group:
 
Where  refers to the determined monthly imbalance of a metering point „i“ within the second (annual) imbalance settlement, and „N“ refers to the total number of metering points which belonged to the balancing group in the specific month.
Imbalance of a metering point in a calendar month equals a difference between realisation in the second (annual) imbalances settlement and the first (monthly) imbalances settlement:
 
where  refers to the (calculated) monthly realisation of a metering point within the second (annual) imbalances settlement, and  refers to the determined (calculated) data on monthly realisation in a metering point within the first (monthly) imbalances settlement.
Unit price for each month in the second (annual) imbalance settlement for positive and negative imbalances equals average monthly reference price of the first (monthly) imbalance settlement.