system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why Tesla's new power wall a big deal.

How is Tesla's new battery pack much different from what I can get today?
gpt
For people with solar panels, it lets them store the excess energy and use it themselves rather than selling it back to the grid for pennies.

For everyone with variable usage costs, it lets you take power from the grid when it is cheapest (nightime) and then store it to use at any time you want basically meaning you always pay the minimum rate for your power.

For everyone long term, if these gets widely adopted, power companies can completely change the way they create power, and there will never be variable rates. And "theoretically/optimistically" power would get cheaper because power plants would be running constantly rather than stopping and starting.

Telsas power banks are better than what you can get today simply because they are for the most part a lot cheaper than current methods, and have programming built in so anybody can use them efficiently.