When I put up the solar testbed I realized it wasn’t wven close to a good place for solar panels. It was just convenient. As winter moved in I noticed the angle of the sun was lower than I realized. On November 16 I decided to angle the panels a bit more toward the sun. This led to noticably higher peaks on sunny days.

The panels were also close to the east side of the house which put them in the shade most of the afternoon. So I bought an extra 20 feet of wire and moved the panels east a bit. This was on December 7. Unfortunately, many of the days have been cloudy, but the chart below gives the output per day. And even as I moved the panels to get more sun, the days got shorter and the sun lower in the sky. But I still was able to see a new peak output.

Some points. I learned that angles aren’t as important as I expected. In fact, panels that track the sun gets maybe 20% increase in output. Not trivial, but probably not worth the effort in most cases. And since the angle of the sun varies so much over the year (and through the day!) the angle for a fixed panel is just a sort of compromise anyway. So mostly people just go with whatever angle their existing roof is (of course). One thing that I didn’t appreciate was the effect of shorter days in the winter. There are some calculators on line that let you play around with this but the longer days in the summer make a big difference. Finally a good sunny day is really dramatically different than a cloudy day. All of this pushes toward larger panel arrays and larger batteries for going completely off grid, depending on where you live.

The last bit has to do with the way output is measured. In the graph below the shaded boxes at the top of some of the bars indicate different battery charging modes. So the days without these shaded bits are days the battery doesn’t fully recharge. This also brings up the point that output is just what you use. Unless you completely drain the battery, this isn’t showing the actual (potential) output of the panels. I tried to put some larger loads on sunny days to see what sort of peak I could get, but even that is hard to plan.