We found with 400 watts, 5 12 volt wet batteries, flat mounted on the roof and with not the most expensive controller, that if we're in a spot with decent sun exposure, and if we shut off the inverter at bedtime so as not to run the residential fridge all night, we need about 2-3 hours of generator time for a weekend.
The panels will charge the batteries all day but not enough for a full charge. When I upgrade to a DP
I'll go up to 500 watts with a better controller and 6 volt batteries...