I have an 8.6k system on my second floor roof and is facing directly south, 12* off of perfect solar south I am told.  The roof angle is 8 in 12, don't know what this is in degrees and no shade on any panels.  I live in New York state in the lower hudson valley region (by West Point).  My question is whether there is any point in the year when I can look at my inverters and see that they are generating the max of 8.6k?  I check them on June 22 at 12 noon (perfectly sunny at the time), the closest the sun is all year, and it was not maxed out (it was at about 7k at that moment).  The best day that I have had was 53k generated.

That doesn't sound too far off. You have to remember that to get the optimum output you would have to be at the equator on the solstice at solar noon and with the panels at 60F, not very likely. My max output tends to be in the spring, April or May, when its cooler and full sun, as it warms up the panels drop off in output. I only have a 1.8k system and usually see about 1.5-1.6k at solar noon.

It does sounds like your tilt is low, it should be your latitude +15 for peak winter or you latitude for peak summer output. An 8 in 12 pitch is 30* (I think) and I think your about 40* north. It might get you another 10% to tilt another 15* or so, but depending on your mounting it might also shade the panels above them in winter, which would be much worse.

Thanks Brock. I thought that was the case. I just needed a sanity check.

Simple solar geometry (latitude +/- 15 rule of thumb) is WAY too crude a metric, since local weather, panel temp, seasonal air-clarity play a significant role. Summer haze in the Hudson valley cuts into the theoretical maximum. Collector outputs are rated at 25C (77F), and efficiency falls with temp. Collector temps are typically 20F above ambient, and I'm guessin' the mid-day temps on an average day in late June are already way over the 77F mark.

Crisp winter air with cooler panel temps and high reflectivity snow can give you higher than anticipated winter returns. Seasonal dust/pollen on the collectors is a real issue in some areas too.

To figure the optimal angle for your location, read & understand this:

http://www.hawaiirdp.org/hetl/AdvisoryGroup/tilt-az-paper-3z13.pdf

Interpolating from the contour lines on figure 9 (p6 of the PDF pagination), it looks like your optimal tilt is ~33degrees, so at ~30 degrees you're close enough to perfect- just a bit off the bullseye on azimuth and dead-nuts on the optimum for that azimuth shift. Moving the tilt 15 degrees would REDUCE, not increase your annual take by about 10%.

Not to worry; I live in So. AZ and have 3.6KW system; the best I have ever seen was 3.4kw;

my supplier said I would lose 20% thru the inverters.

applying that to your 8.6=is a loss of 1720=net maximum of 6880; so 7K is a good read.

My best reads come in spring and fall.

Very likely due to the derating due to temperature effects you suffer during the summer.  In NY I'd expect output to in the spring, before the summer humidity shows up.