After a year-and-a-half, and correcting for the current SOC of 1.8 kWh stored, my stats areThanks mikemillar, my initial reading based on 4 days and a total export of 7.3 kWh says my efficiency was only 75%.
"energy_exported": 6319520,
"energy_imported": 7035558.2, efficiency 89.82% (close enough to 90% for my purposes).