Levelized cost of electricity, to calculate the absolute costs?
In general, an LCoE forecast for a year, is the unit cost of electricity for generators that come online in that particular year. 

Whereas, for a given year's (e.g. 2030) forecast of the cost of electricity, the average unit cost of electricity is a volume-weighted arithmetic average of the levelised costs of all the generators that have been built previously, that are operating in the forecast year. Typically, those generators will have been built in the previous 20 years.

That's not the only challenge:


you will need to check the actual definition of the LCoE data that you have. It might be the unit cost for generators that get their Final Investment Decision in that year (and so will come online sometime later, probably in the range of 1-15 years)
usually (but not always), changes to the underlying cost will affect total demand, so you've got a two-way feedback mechanism between quantity and price.
that rate at which things are deployed, and the consistency of speed with which they are deployed, affects their LCoE. There are chokepoints in various supply chains, there's exogenous and endogenous cost reductions from learning by doing, and so on.
merely averaging all the individualised costs of energy, omits the costs that are borne by the system itself: the cost of transmission and distribution networks, the costs of storage, and the costs of mechanisms to keep demand and supply in perfect balance every 20 milliseconds (or so) of the year.


So you can take historic LCoE, and multiply it by the quantity of electricity demanded in a year, to calculate total cost of electricity consumed in that year, subject to the above caveats. Note that that will give you a different answer to the amount of capital investment needed.