I have a totally different view on this. I run my system at a fixed power point voltage with an arduino. I live successfully totally off grid for a little over four months in the summer with only a car battery. This system provides refrigeration, lights and all hot water. My take on efficiency is different. 40 years ago I made a machine that was the fastest in the industry. It didn't matter at all. In a 12 hour work day it only ran for 4 hours. The same problem exists in solar. A minimum number of panels is needed to operate through the worst days. On other days There is excess energy that could be used and it is just wasted. My system was a test bed to show solar could be implemented very cheaply, basically only the expense of the panels. If what I do seems a little odd, it is not because I don't know better. As it turned out, I don't see much reason to change it. It won't be long before solar equipment joins the other compost of our electronic society. I'll certainly upgrade when this free stuff becomes available.
The power point of a panel is pretty much dependent on temperature. During one season the temp doesn't change that much. It does during the day. Mornings are colder, but there isn't much power there. At peak sun times it is hard to put that extra energy someplace useful. I have a chest fridge that I fill with a lot of liquid. I store cold through the night. Fridge operates in a very tight band just above freezing. It only operates when the battery has a pretty good charge, about 13.4V if I remember.
The arduino is the charge controller, a simple buck converter off the 36V string with about a 51V power point. Charging the battery has priority above all else. The battery can be thought of as the fridge. The converter is less than 180W on a 900W array. Don't laugh, PWM is at 120Hz using power transformer as the inductor. The losses don't really matter, it is a part that anyone can find. All I need to do is power the fridge real time. The excess power is fed to two water heaters. I can generally dump 2.5KWH to heating water a day. These heating elements are PWMed from a large capacitor bank, the same that feeds the converter.
The program decides where to send power based on the buss voltage. This year my wife wants a dishwasher and I will be doing that in time slices. Doesn't matter if it takes two hours to do. The display for the entire system is just two blinking LED.
What I am trying to say is that it should be looked at as an entire system, not a bunch of black boxes slung together. I see enormous energy waste in most RE systems. Battery storage makes every system cost ineffective.
