John & Nick:
The challenge with talking about solar "output" is that what really matters is amp-hours or (watt-hours). You might get even the full rated power of your panels briefly.....but if you only get it for 10 minutes, it doesn't do you that much good. What matters is how much you get over the longer term. I'm not in the Chesapeake--we're near Seattle--so my numbers won't be particularly useful to you, but I'll share some planning numbers that might be helpful.
There are a variety of "rules of thumb" out there that are used when planning a solar array for a boat. Most of the published rules I've read say plan on getting between 2 and 5 hours of the full rated output of your panels each day. Obviously, your mileage may vary....
So for example, I have 2400 watts of solar panels (6 panels x 400 watts each). Using rule of thumb #1, I'd get 2400 watts x 2 hours = 4800 watt hours that equates to about 177 amp-hours @ 27 volts of charging voltage. If you increase the multiplier to 5, that works out to be 2400 watts x 5 hours = 12,000 watt-hours = 444 amp-hours @ 27 volts.
My practical experience (now 2 full cruising seasons between Seattle and Alaska) is somewhere in between these two numbers:
I have a 1600 amp-hour house battery bank and we typically run it down to maybe 60% overnight. I start the generator in the morning and run it for about 2 hours to get the bank up to between 85% - 90% (roughly 400 amp hours of charge). Exactly how long I run it depends on how much sunlight I expect that day. On a nice sunny day, the solar panels will finish the last 10-20% of charge, so I will shut the generator down at about 80%. On more overcast days, I may just barely keep up with the load until late afternoon or early evening when the sun gets too low in the sky.
If we didn't have the solar panels, but about 8 pm, we'd be back down to about 70%, which would mean that we'd go below 50% overnight (I still have AGM batteries, so I try to avoid going below 60%, but 50% is my lowest case). That usage over the day (say, roughly 20%), suggests that we use about 320 amp hours over the course of the day. (We have lots of refrigeration on board.....so we're kind of power-hungry).
So.....if we assume that my array can produce something on the order of 200-300 amp-hours/day on a typical summer day, that falls in the middle of the two rule of thumb numbers above. If you pick the middle value (250 amp-hours), that works out to be 6,750 watt hours (250 amp-hours x 27 volts = 6750 watt-hours). That is equivalent to about 2.8 hours of full rated output from my panels. (i.e. 6750 watt-hours / 2400 watt panels = 2.8 hours of full-rated output).
While I haven't kept really careful records, I think the highest instantaneous output I've seen out of my 2400 watt array is about 1800 watts for relatively short periods. That seems entirely reasonable to me just because it's almost impossible to have zero shading on the panels from other stuff up on the hardtop and surrounding trees, etc..
So.....I hope that helps and not just "muddies" the water......
Mark Tilden
Selene 60 "Koinonia"