Well Doc,
The only real thing to consider is how much you want to spend.
The problem is that the 1~3 Days 3~4 times a month looks a lot like continues to the house bank. If the 3 days comes right after the other 3 days, that is really tough for the sun to make up.
Were I in your place, I would start with as much PV on the roof as you can justify. Then shop the market for charge controllers. Those will be your not-so-secret weapon here. There are two basic types: Maximum Power Point Tracking (MPPT) and the industry-standard Pulse Width Modulation (PWM).
All of these are better than they were when I was working this market. If I was to try to recommend, the model would be obsolete by now. There are many that will do a good job of changing without damaging the bank.
Matt
