A calculator will fail, as in order to use one, requires knowing all of the terminology, and how each variable, alwase effects the other variables in power claculation, and if you know that, the claculator is redundent. My first PV/battery off grid experienxces were in the early 90's, and I was gifted a small solar panel (5w), from a teacher, who had 2 100w panels purchased from the worlds, first and at that time only retailer of PV panels. Today the challenge is to make a system "plug in and forget", and the tech is not, quite, there. I have a whole bunch of random, solar, pv, back up, and UPS, stuff....that keeps comming my way, and I repurpose it for secondary and utilitairian uses, my main house system bieng much larger. And to fair to you, marketing and splianing the solar,pv,battery thing, is a swamp. I had a 92 dodge diesel, the "truckasaurus" that I covered the very large hood in solar, put in a big battery bank.....removed the alternator, and drove it like that year round...in Canada. It would reliably draw a crowd,and became localy iconic, so I have fielded all the questions and seen the hope in peoples faces, and faced the anti solar bunch. My house set up is also highly visible, also bieng a conversational/ideological subject. I can see that your system has the plug in and use part taken care of, and a lot of the pieces for marketing, but determining the crossover point between peoples expectations, and actual performance will determine continued sales success.