To add, the 300W of AC output would be pulled from the 100% batteries until the state of charge goes down to 99% and then your AC300 would pull from solar to re-charge the battery and this would repeat.
The B300 battery is rated at 3500+ Cycles to 80% of original capacity. If you charged it and discharged it once a day, you would go through 3650 cycles in 10 years. By that time you’ll likely see even better energy storage technology.
I suggest investing first in a Kill-a-watt or similar watt meter device which measures your power usage over time in kilowatt hours. For example, your maximum power consumption at a given point in time might be 1500W but is that all of the time? If it’s all the time then it would use up all the energy in a single B300 battery in less than 2 hours (3000Wh * 0.8 inverter efficiency loss / 1500W load = 1.6 hours). A second example is if your average load is 500W then the calculation would be 3000Wh * 0.8 inverter efficiency loss / 500W load = 4.8 hours.
Thank you for the answer.
I am using Schneider PowerTags to measure my usage. The current load is around 800-900W, but I plan to upgrade, and the max would be 1.5kw 240V. But is it correct that I can only use 80% of the B300 battery power? Same as with UPS?