in other terms electricity systems are lockedin with their existing generation mix and cannot quickly adapt it to changing market conditions in discussions about the costs of backup capacity this is also referred to the ex post case in the long term instead electricity companies can adapt their generation mix to new market conditions resulting from changes in demand fuel prices as well as the introduction of new capacity into the electricity mix this was referred to as the ex ante case as the analyst places himherself at the very beginning of the investment cycle which can now be optimised