Utility-scale energy storage is mandatory, in order for large scale wind and solar power projects to be made viable as baseload power. Sodium sulfur batteries have been the front-runner for utility load-leveling and large scale backup, but if Altair's new lithium titanate batteries can outperform the NaS batteries at comparable cost, there may be a new, better utility storage "sheriff" coming to town.
As for trying to park four semi-trailers in your backyard to provide a month's power backup for your home, better reconsider. If you have to ask how much these high-performance batteries cost, you can't afford them.
These aren't intended for residential or other non-commercial applications, though there seems to be a reasonable expectation that their capability isn't out of the realm of possibility for such uses in the next few years. Which is good, as it appears we may well be able to afford to recharge them after all.
Exciting times we live in.