I like the idea and would probably reserve some if I still lived in the US.
But I don't think you should be setting yourself up against Powerwalls so directly. You're not really competing for the same market. The power storage solution for the 99.7% of us without Powerwalls is in fact Powerwalls (or similar) if you have solar panels/want a serious amount of backup power storage.
Your offering is not that. In fact, I can imagine some people with Powerwalls might want to add your product to their house as well, so no point in immediately turning off that 0.3% in your messaging.
But I don't think you should be setting yourself up against Powerwalls so directly. You're not really competing for the same market. The power storage solution for the 99.7% of us without Powerwalls is in fact Powerwalls (or similar) if you have solar panels/want a serious amount of backup power storage.
Your offering is not that. In fact, I can imagine some people with Powerwalls might want to add your product to their house as well, so no point in immediately turning off that 0.3% in your messaging.