It would easily run me $10k to do all this, before I was able to cross tie a single kWh. And, in the bargain, I'd lose the standalone power system that is my office, because getting battery backed stuff approved out here is basically impossible. I tried for the house system, and after 18 months of fighting red tape that exists to fund the red tape, I gave up and built a grid tie system without a backup.
I get that it sounds easy, but it would cost more to interconnect it than the standalone system cost in the first place, drop me out of a very sweet 25 year net metering grandfathering, and leave me with a far less capable property in the deal. Sorry, just not interested in that.
I get it. I have a solar system too and there's no way in hell I'm updating it.
However, my system is also rather a good bit more reliable than the grid power on the house, which is nice for remote work.
I know you said grid-tie isn't worth the trouble, but until the USA moves to more renewable energy for power production, that might yield the best carbon reduction, depending on how much you could otherwise sequester per KWh.
The national average CO2 emissions for power production is 947.2 lbs CO2 per megawatt-hour [1] (or 0.947 lbs/KWh).
So unless you can sequester 10-15lbs or more of CO2 a day, then you may be better off sending your excess power to the grid if your goal is carbon reduction.
Though I'm not sure how to account for the actual CO2 reduction - is the national average fair? Should you use the average per state since states vary widely in their renewable energy status? Is there some other way to determine how much CO2 you've offset?
[1] https://www.epa.gov/energy/greenhouse-gases-equivalencies-ca...