I have the Fridge inverter 1000W and the whole house inverter 3000W. My battery monitor Victron 712 or a Smart Shunt tells me I am using over twice what the refrigerator draws when the house inverter is on all the time. I am glad I have both. If you do not have something to monitor the Amp Hour current draw I highly recommend it also. Battery voltage is not accurate readings. AGM batteries can only be drawn half way without doing damage so your usable amp hours is just under 450 amp hours usable.
Here is a good article on battery usage and charging.