[Guvante]

The fact that an arbitrage opportunity will not always be available does not mean that arbitrage opportunity does not exist.

Also electricity companies would be very slow to adjust to reduced demand by lowering prices, making this work for longer than a naive analysis would predict.

[hueving]

>The fact that an arbitrage opportunity will not always be available does not mean that arbitrage opportunity does not exist.

Spotting a leftover cookie on the table means you will probably be able to get a free cookie. It doesn't mean that you have found a way to solve world hunger.

[Guvante]

Everything you have said can be said about literally every possible opportunity to make money outside of those that leverage sweat equity.

If you want to say something about his idea that is specific you could add value.

For instance attempting this arbitrage is a risk transference since you are betting that the technology of batteries won't catch up before you have made back your capital investment.