I happen to be in the solar business, while great as a net metered solution to save on you electric bills, conventional solar will only work when the grid is operational. Otherwise you would require an inverter and battery backup system that run at all times to keep the batteries charged. The DC voltage direct off of a solar panel is far to volatile otherwise. by law when a grid failure occurs the power from a solar system is automatically disconnected from the grid, the reason behind this is that the current created would flow back into the grid charging the utility lines. This could mean electrocution for anyone working on the electric systems.
The maintenance on the batteries alone would be significant. Granted our tanks aren't using huge amounts of power, my money would be on a generator, much more cost effective for this scenario.