Both sources take the interview out of context. Immediately after "Yes, they do," Granholm corrects herself:

TAPPER: Do you think that adversaries of the United States have the capability right now to shut down the power grid? 

GRANHOLM: Yes, they do. 

I mean, I think that there are very malign actors who are trying. Even as we speak, there are thousands of attacks on all aspects of the energy sector and the private sector generally, I mean, the meat plant, for example.

I know enough about both hacking and the power grid to know there are a lot of smart people at the North American Electrical Reliability Corporation (NERC), the Federal Energy Regulatory Commission (FERC), and various regional regulatory agencies who have considered how hackers might disrupt the U.S. power grid, and put substantial safeguards in place.

If adversaries could take down the U.S. power grid right now, they would have done it. That doesn't mean, however, they won't be able to do it tomorrow.