cracovian said:
It's fascinating stuff about the sun. I really expected my summer current and total production to be off the charts and here you are blowing my bubble :-( What's next, you're going to tell me that it's the Earth revolving around the sun and not the other way around?
:lol: Your ENERGY production will absolutely be maximum during the summertime. But that is due to the long days with the sun almost directly overhead. But your instantaneous POWER production, which is what an inverter might limit, is the LOWEST during the summertime for two reasons: high PV module temperatures and the sun never passing through (or even particularly close to) the boresight of the array. The entire discussion revolved around whether or not you could get away with lower-power inverters in your application to save some money without hurting yearly ENERGY production.
cracovian said:
I'll measure my tilt tomorrow - I'd love for you to comment on what it means depending on the seasons. To me it looks like an excellent tilt!
I think the tilt of your roof is very nearly optimum for solar production, assuming the roof is anywhere close to pointing South. My favorite site for determining optimum tilt for a given location is
Solmetric. If your roof is really 7/12 pitch, that is 30.3 degrees elevation. If the azimuth of your roof is between 165 and 200 degrees, then you are within 1% of the production you would achieve with optimal pointing!
cracovian said:
I do get your point about the inverters and thirty bucks is thirty bucks. But then you also told me not to go with lower-rated panels. That would mean a difference between $185 250 Watt Suntechs vs. $336 280 Watt LGs for example... It seems (falsely?) like a bigger waste of money though those LGs sure look purty
Wow! :shock: I hadn't looked at prices and I did not realize that moving from 250Wp to 280Wp changed the price per from $0.74/watt to $1.20/watt. But that is why I included the caviat: "More is better unless you are paying a fortune per watt." I would agree increasing your $/watt by 64% qualifies as a fortune! That is clearly one reason your system was expensive. So, yeah, if you can save a lot by going with smaller PV modules, then definitely reduce the microinverter to the M215 at the same time. But note that energy production changes proportionally with the PV module rating, so a 250Wp panel will only harvest 89% as much electricity as a 280Wp panel. By contrast, with microinverters going with the larger power rating has almost no effect on energy harvest.
To that point, please note that over the past three days, November 20 through 22, even though you have had completely sunny weather and no clouds, the M250 microinverter has resulted in zero additional energy harvest versus what would have been produced with M215s. You can see this by noting that not a single one of the 15-minute production periods in the "Hourly" plot on your site exceeded 450Wh during those three days.