>A 2014 Congressional report found that if more than eight transformers in the United States were destroyed simultaneously, the country’s entire grid system would collapse. Since it can take up to 20 months to build, test, and install new transformers, many areas could see extended periods with reduced grid power, or even none at all.<p>This is the scariest fact here. Even if we hardened against CMEs, there are other things that can threaten transformers(terrorism, extreme weather, etc). If it takes 20 months to replace these kinds of things(assuming you even have power to manufacture them), then we should have a backup supply. Ideally at least one for every one in operation.