I had some Prestige pans with a lifetime guarantee, the company was taken over, needed new handles and knobs.It depends, many factors to consider. This is our forever home so the investment is worth it. We already have solar panels installed and they work from daylight, not sunlight. Obviously, brighter the better but will still work.
Warranty is 10 years with the powerwall, but even then the internal batteries can be changed very easily (effectively AA sized x lots). The wife drives an electric car and if we do get the power walls then I will also get one. Capital costs aside, free electric means free fuel, free heating + cooking, lighting etc etc
You’d need a lot of careful calculations on such a thing and if generating our own power was worth it there’d be no power stations.