400 watts in panels make 480+ watts of power. Can you explain that?

[Q-Dog]

I have 4 X "100 watt Windy Nation slim panels" and Victron MPPT that I have observed several times now to put out a fair bit over 400 watts. Highest ever was 485 watts and many times over 460 watts. 2S2P configuration into a 100/20 MPPT on a 24 volt system. My best solar day so far is 2.90kWh from 400 watts of panels. Is this what I should be expecting? Was thinking to add a couple more of same panels, but with this output not sure the MPPT can handle them.

At first I thought maybe I was picking up reflection from the house, but I put the panels out in the grass and had similar output. I have been trying to figure out best location to install panels on my non-optimal roof, so I made a small rack that I drag around the yard to find best location.

The plan is to eventually put these panels and charge controller on my RV, but for now I have them adding electrons to the battery backup I built for my house.

So, is this normal? Everything I read says the panels likely won't ever make their rated watts.

 

[LeRoy Christensen]

What's your make of panel? Sometimes in very cold environments panels can produce more than rated watts. In testing new panels that are not reaching rated capacity I spray cold water on back to see if they meet specifications. If not I return them as substandard.

 

[Q-Dog]

Windy Nation 100 watt Slim Panel.

Today is mostly cloudy but this was moments ago:

 

[jtvt]

My 170w suntechs produced more than rated when they were new. I haven't really payed attention recently. My theory is panels get rated like CPUs. They make a batch and test. Some will rate at 165, some at 170, some at 175, etc. Sometimes they take a 175w rated panel and sell it as a 170w panel so there is stock of 170w panels to sell. Plus also the test performed doesn't really represent real world usage. There are also "edge of cloud" scenarios but those should be fleeting and likely not even visible on the display.