When describing commercial risk it is convenient to consider its relevance to three aspects: (i) overnight costs, (ii) financing costs, both of which apply during the construction phase, and (iii) the business case once the plant is operating.

Overnight costs

The overnight cost data presented in PCGE suggest that uncertainties in cost estimates for nuclear plant are no bigger in percentage terms than those for gas or coal. When thought of in absolute terms, however, they are significantly greater for nuclear than they are for coal or gas. Consequently, nuclear is the most sensitive of the three to inaccuracies in estimates of overnight costs. This represents a risk that results in all kinds of sophisticated analyses being brought to the problem including probabilistic assessments to obtain more robust cost estimates. Ultimately, however, what is needed most of all is practical experience of NPP construction. The hope is that, as more of them are built and as designs become more standardised, estimates will become less subject to error and contingencies will be reduced.