1800 should do you for what you are saying just fine, but 140 amp is really not a lot. That is where your 6v batteries come in to play, my two have 230amp for 12v. I have a formula for figuring that out somewhere, I'll try to find that for you, but none the less for the short time your talking you should be fine. I only have 1000w and my wife watches until she falls asleep, then I reach over and turn it off
, at sometime during the early morning. Then by late morning the next day my batteries are right back up again - solar.