If the feed-in tariff is high, then no battery technology is viable, because it is too expensive.
I don't think so.
There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.
Both could make economic sense, or could be uninteresting, depending on many local factors.
But the cases where it makes economical sense are probably still quite niche today.
But two factors will change that :
- Sinking battery costs : Li. Batteries prices drop 30%/Year
- Scaling up of EVs : the adoption of EVs doubles every year, and those can and will probably be reprogrammed as grid stabilization batteries.
In a few years, batteries will change the landscape of electricity pricing and costs.