I’m not new but haven’t been here in a while

[Grampasteve]

I’ve had PV since 2009. It was a 5040 watt array on the garage roof pointing almost dead South. The roof had a 5/12 pitch. The panels were Solartech. The Fronius inverter was in the garage. I would look at the wattage display on the inverter a lot at first and later occasionally when I walked through the garage. On at least 3 o assigns the display read a higher wattage than the array rating. Not a lot more but readings like 5110 or 5087.
then in 2019 we sold the farm and moved closer to town and installed a ground mount array rated at 8900 watts. The array pitch is 5.5/12 and is due South. The panels are Trina.
i have a solarEdge inverter and an app on my phone that tells me at any time the production of the array and also tells me the maximum production. The highest production from this array I have seen is 8014. That’s not even close to the rated output.
my question is why does this new array not even come close to its rating?

[J.P.M.]

I’ve had PV since 2009. It was a 5040 watt array on the garage roof pointing almost dead South. The roof had a 5/12 pitch. The panels were Solartech. The Fronius inverter was in the garage. I would look at the wattage display on the inverter a lot at first and later occasionally when I walked through the garage. On at least 3 o assigns the display read a higher wattage than the array rating. Not a lot more but readings like 5110 or 5087.
then in 2019 we sold the farm and moved closer to town and installed a ground mount array rated at 8900 watts. The array pitch is 5.5/12 and is due South. The panels are Trina.
i have a solarEdge inverter and an app on my phone that tells me at any time the production of the array and also tells me the maximum production. The highest production from this array I have seen is 8014. That’s not even close to the rated output.
my question is why does this new array not even come close to its rating?

My initial guess is that your optimizers are rated at something like 90 % or so of your panels' STC rating.

[J.P.M.]

[QUOTE=J.P.M.;n443538]

My initial guess is that your optimizers are rated at something like 90 % or so of your panels' STC rating. That's a pretty common/approximate scenario.
QUOTE]

[Grampasteve]

Is there anything that can be done to get closer to the STC rating

[J.P.M.]

Is there anything that can be done to get closer to the STC rating

Short answer: Yes but not without changing some equipment, either smaller panels or bigger optimizers.

You may be under some misapprehension that a system's possible maximum steady state and useful output is higher than it is.
The situation is somewhat, but not entirely, analogous to a vehicle with an engine rated at 300 HP, but most of the time the engine operates at a fraction of that output, and because of system (mostly friction) losses the 300 HP max. engine output will never be delivered to the ground by the wheels.

Since optimizers are usually and for most applications most likely correctly sized to have less output capacity than the panels they're connected to, I've long thought that a residential system equipped with optimizers ought to be rated and sold by the optimizer size rather than the panel STC rating but I'm sure that would go over with the solar peddlers like a fart on an oak pew in church on a Sunday morning.

What you may be missing here is that a PV panel or a whole system's output is changing constantly and will most likely spend very little, if any, of its life - at most something like a small fraction of 1% of its life operating at anything close to 90 % or more of its STC rating and usually much less than that, like from zero at sunrise/sunset to some daily instanteneous maximum of maybe 60-85 % or less of its STC rated instanteneous output, the lower 60% output in winter, the higher output probably in spring/summer on some days.

I keep pretty good records and tabs on my 11+ year old system. The highest steady state (continuous) cloudless, clear sky output I've seen or recorded is 4.55 kW out of my 5.232 STC kW system, and that was with an array that was cleaned that morning.
Those types of very high clear sky steady state readings at my house greater than ~ 0.85 of STC rating are somewhat rare and generally in March or April under clear skies with a brisk wind, a clean array and around the time of near normal solar angle of incidence relative to the array with relatively low ambient temps for this area.

I have seen and recorded instanteneous system outputs in excess of my system's 5.232 kW STC output (highest was 5.36 kW) under non-steady state conditions such as partly cloudy skies with brisk wind and clear air just after a large cloud has passed by at close to the time of minimum solar beam incidence angle on the array.
However, those types of non-steady state conditions readings almost always persist for what's usually much less than a minute, usually for about 10-20 seconds or less.