Severe Space Weather Events–Understanding Societal and Economic Impacts (2009)

One of several studies on what would occur if a Carrington-level event occurred today.

See also the OECD's report: http://www.oecd.org/governance/risk/46891645.pdf

The remarkable thing is that it would cost in the low billions to safe the United States' EHV transformers, which are the most difficult components to replace, but I suppose we simply don't invest in infrastructure anymore.