Well, I have to disagree with some of the opinions given here. I have two panels with a combined rating of 370 watts. Panels are 11 years old. On a recent trip to Wyoming this summer, I recorded 411 watts output. Of course I had some ideal conditions beyond the standards by which panels are rated. I was at about 9000' elevation and the wind speed was greater than 1 m/s. However, the temperatures were much higher than 20C and though the panels were tilted somewhat toward the sun, certainly weren't perpendicular to the radiation. I often see peak watts greater than rated panel output.
