You can do a lot with 78 megawatts, including power 26,000 homes, for instance. Or you use it to run absolutely everything on one of the Navy's newest warships.
I'll let IEEE explain:
The Zumwalt’s propellers and drive shafts are turned by electric motors, rather than being directly attached to combustion engines. Such electric-drive systems, while a rarity for the U.S. Navy, have long been standard on big ships. What’s new and different about the one on the Zumwalt is that it’s flexible enough to propel the ship, fire railguns or directed-energy weapons (should these eventually be deployed), or [all] at the same time.

