Portable panels can be highly-productive and useful, but good results require owner discipline.

Rated watts are rated watts; a 100w portable will make the same power as 100w mounted in a lab.

Portables can outperform flat-mounted panels when they are either

• set out facing ~south¹⁾ at seasonally-optimal tilt; or
• moved throughout the day to optimally face the sun. This can increase harvest over fixed tilt but requires frequent repositioning. To give you an idea, automated single-axis trackers that follow the sun automatically can increase yield over fixed tilt by 20-35%. Increases from occasional owner repositioning will be lower.

• owners not setting them out for whatever reason ←- the biggest issue
  • laziness
  • “won't be here that long”
  • panel isn't waterproof and it might rain (or has rained)
• set out but fell/blew over face-down
• set out in overhead shade or high grass shade
• set out facing north (!!) {“as I write this there are two rigs in my line of sight with this unforced error.” - secessus} Note: setting out facing east or west can make sense if direct sun is only available in that direction, or if one is manually “tracking” the sun.
• made of “flex” crystalline that breaks
• loose dogs pissing on them