According to Hobotech tests. 16 hours @ 8Amps x 12volts = 1536 wh. The AC200 Max is 2048 wh so you will lose 512 wh on overhead. Total 25% due to overhead. This is where all the power is gone.
|HOBOTECH
Watch again. My DC test takes 16 hours and runs 8A.
It is pretty normal to loose 20% in battery to output due to voltage conversion inefficiencies. The AC200Max may have some fancier electronics and such. 20% loss is standard, especially when running AC. 15% is good. 25% aid a little high, but nothing crazy.