I have 800w of solar and 600ah LFP. I thought I would be net-zero. Ha!
Backing up in the thread:
I have 640W of solar and have 5 years experience of their performance in Florida Keys and Bahamas while 100% at anchor or on a mooring. This time of year if everything is perfect (full sun, panels facing south and not getting any shading) I can count on getting 120-150ah out of the panels (12V system). I norm for planning is about 100ah can normally be counted on. But by Mar/Apr I can count on getting 200ah out of them under same conditions.
Now I only have 1 season of use with the LFPs. It may be I get more power out of the panels on a day that was perfect and the SOC was low enough to take all the power all day the panels can put out if there was a place for it to go (my solar controller logs all this data). I don't know.
The reason I don't know is that I still have too much acid battery experience inferring with my mind. So on cloudy days I have still been running the generator to keep batteries from going below 60%. I don't know if I have have been worried about going low, or if it is just a "I would prefer to listen to the generator for 1 hour/day instead of for 3 hours/3 days.
So much about the whole thing revolves around how you operate your generator runtime for other reasons. Do you run it daily for hot water? Do run it every 3-5 days to run the watermaker (I run my watermaker every 5 days because it seems wasteful to flush it just to run it a few days later). For the powerboats do you run it to power the stove? Plus for me it is still hard to accept not worrying about having a high SOC.
I recently let my LFP get to 15-20% to see what would happen. It was hard on my acid battery trained nerves. But now I know for a fact instead of "on paper" that that was OK. I recommend everyone with LFP let their batteries run down and find out it is OK. When I did my it was cloudy for like 4 days and I barely made any solar and at the end still had to force the charge down by turning on every DC load I could.
Over the years I have learned the happiest cruisers about their batteries are the ones that don't know anything about them other than if the voltage was OK. That is almost where we need to get our minds to for LFP house banks.