We've looked at the Cummins-Onan 3KW RV generator, as well as the little Honda 2200i, and the numbers only work if you're not doing full-time self-supported RV living. Around 3-5 years in, the fuel costs for the generator exceed the additional expense of a large solar system.
You have a disconnect here, I'm not talking about replacing your Solar Panels w/a Onan Onboard genset.. You keep your solar panels on the roof and instead of using your drive engine as a backup charge source you use your genset, you can still use your drive engine when driving, but when your parked thats just terrible for it.. since we're talking backup power source, even in 3-5 years full time your talking less fuel use than you'd of got idling a big military engine for the same purpose..
Solar is not a panacea, even with massively oversized solar there are times of the year where your only getting a small fraction of its output, an inch of snow on the panels? 0W out of your 2kw solar.. parked in a forest with overcast? 200W would be 10% output which is what you get in diffuse/shaded output.. then you got winter where the sun is low in the sky, the angle of attack is almost always coming through trees, or hard to break into a valley.. you might be lucky to see 10-20% output of that big massive solar setup.
A generator for backup when the sun gods have forsaken you is better than a military drive engine as far as efficiency is concerned, and your going to be relying on it here and there alot more than you think.. but with a fast charging bank, your talking like 2.5-3h of runtime to get you from empty to full, thats nothing really in grand scheme of things.. if your 6-7h of genset a week in bad solar, and your at like 40% bad solar days a year thats a mere 156h of runtime a year to fill the gaps.. after 5-6 years your backup power system will be still under 1000 hours.
Then this double wammy's your aircon issue, if you only use it on rare occasion.. just use the damn generator on occasion and the deal is done..
You have to totally ignore all the solar calculators you find online, those are for fixed installs.. you know, where you chop down some trees and make a clearing that has ideal sun exposure all year long.. your mounting em all to your roof and living a nomadic lifestyle, your never going to be able to predict the weather and location and how much sun you get or anything.. I think its awesome your planning for a mega 2kw solar build, but only because its so overbuilt that in tough solar conditions.. even at a 10% output in cloudy conditions, your getting more than most of us here do on a perfect day on the summer solstice.
Gotta plan for the worst and hope for the best, and its one of the strong advantages to LFP banks.. you can overbuild solar so much that those bad days you can survive, while still being able to utilize that over paneled capacity to capture short bursts of sunlight coming through the clouds/trees, or just simply burning it on frivolous energy usage when there's more sun than you need.
