Yep and yesterday FullyCharged released a vid about it being on trials - https://www.youtube.com/watch?v=z1Z4JCoPAGc

An interesting note from the video is how they said they could detect the grid frequency from the plug to detect times of over supply and (in theory) that would be the right time to absorb some of that excess.

Some other interesting benefits (mentioned in the comments) about how it can periodically cycle the heat better than traditional water tanks to kill off bacteria.

That's where I got it from. Was likewise intrigued by the frequency remark, interesting stuff.