This section contain the results of the analysis that resulted into the draft IRP 2018 published plan. These scenarios can be categorised into projected demand growth scenarios and key input scenarios. The scenarios looked at some of the key factors such as the use as carbon budget for carbon dioxide emissions reduction, assumed gas prices variation to analyse the impact of changing gas prices, and the removal of annual build limits imposed on RE.

Key assumptions and considerations included in the scenarios modelled and simulated included, among others:

Following the development of the reference case taking into account the assumptions, the scenarios listed were simulated and analysed.

Technical modelling and simulation was performed using PLEXOS software. The objective function of PLEXOS is to minimise the cost of investments and electricity dispatch using complex mathematical models. The cost function is determined by the operational costs, start-up costs, fuels cost and penalty costs for unserved energy or for not meeting the reserve requirements.

Constraints can be applied to the model in the software if necessary. These constraints include, among others: energy balances; emission constraints; operational constraints (limits on generation, reserve provision, up and down times, ramp rates and transmission limits); regional capacity reserve margins and ancillary services; maximum number of units built and retired; fuel availability and maximum fuel usage; minimum energy production; and RE targets.