*Appendix A.3. OPEX*

The operational expenditure (OPEX) of a certain type of power generation capacity at a certain point of time is modelled as follows. The operation cost of a certain type of power generation capacity in year t is expressed as Opex(t) = ∑<sup>I</sup> <sup>i</sup>=<sup>1</sup> <sup>∑</sup><sup>J</sup> <sup>j</sup> <sup>∑</sup><sup>t</sup> <sup>v</sup>=−<sup>V</sup> <sup>∑</sup><sup>P</sup> <sup>p</sup>=<sup>1</sup> <sup>∑</sup><sup>M</sup> <sup>m</sup>=<sup>1</sup> Fmitv ∗ umijtvp ∗ θjp. umijtvp is the power output of plant m, vintage v, in year t, country i, block p on the load, and exported to country j. Fmitv is the corresponding operating cost that varies with v, and θjp is the time interval of load block p within each year in the destination country.
