The feed-in/battery concept is explained in this video: https://youtu.be/veZmzeHnTvs
But it does not apply to standard solar savings.
This is because each kilowatt-hour can either be self consumed or exported. There is no double counting going on in this instance.
For example, if grid electricity is 31 cents per kilowatt-hour and I have an 8 cent solar feed-in tariff and yesterday my solar system produced 2 kilowatt-hours and I exported both of them, my electricity bill would be reduced by 16 cents.
But if today my solar system produce 2 kilowatt-hours and I self consume them both then today my electricity bill would be reduced by 62 cents. The reduction in my electricity bill wouldn't be less than this because I didn't export any solar electricity today.
And if tomorrow my solar system again produces 2 kilowatt-hours and I self consume one and export one the reduction in my electricity bill would be 31 + 8 cents or 39 cents in total.