In a perfect world it is optimum to have all the sametype and rated panels on any installation. In reality, even if you have a mix and match of panels you will increase your output current everytime you add one. People who have existing systems and are either given or find panels at crazy deals will always see a benefit by adding another panel. Yes, certain types of panels will carry more of the load under lighter load conditions but at some point once the line voltage is dragged down to the lowest common denominator there will be a benefit in adding a mismatched panel as opposed to not adding at all. There are some well educated engineer types on this board who are used to working towards the optimum solution. Nothing wrong with that and I commend them for bringing their knowledge to the table. However, many of us are OK with less than the optimum solution and mix and match systems built over the years, although a compromise, generally are fine. eg if someone gives you a poly panel and you have a mono system, whatever, throw it up there, it'll give you more than you had before. Both of our motorhome systems are like that. We have a little over 800 on the big-un and around 320 on the little-un.
