Too early for that. There are barely any products in the market for this. The ultimate proof will be people installing this in their homes for a certain amount of $ and then getting some measurable ROI (also in $).

But do you have reason to be skeptical about the physics? The premise here is brutally simple centuries old physics and engineering that any high school kid should be able to understand. Simple pressurized vessels holding compressed air. It sounds plausible to me that that ought to be dirt cheap to implement with very low tech solutions for pumping and compressing air and storing it in some kind of vessel.

You see people arguing here for an alternative based on Tesla batteries costing in the order of thousands of dollars even for a modest/small setups. It's kind of easy to see that this could potentially undercut that by orders of magnitudes because there are no special/hard to get materials and it's all based on dirt cheap commodities and technology. Pumps, valves, steel, etc.