+1 Month In Review (420W)

Ive been traveling the south western US for the last 6 weeks, and I have never seen over 360W on my 420W panel. I know people will say “85% efficiency is pretty good” but lets be honest… Thats true when your panel is a 500$ panel from amazon. a $1,000 420W panel should be throwing up 400+ all day in this sun. full direct sunlight without a cloud in the sky 340W womp womp.

I give this panel 3/5 stars. If you haven’t bought one yet, consider what I just wrote.

1 Like

360W on a 420W panel is actual use is in fact very good. Panel are rated according to a set of standard test conditions which stipulate strong sun, clear sky and low temperature. Strong sun and low temp do not mix so that is not practical in real life, you will need tropical sun at arctic temp to achieve STC rates performance (not happening). Thus under realistic conditions, bright sun, normal temp (but the panel is hot due to sun) most panels do maybe 80% of rated. The fact you got 85% in a hot climate very good.

My roof top panels are rated 340w each, but the normal max on a very good day (cool day in May) is only around 280-290W.


The reduced output is probably due to temperature. Solar panels work best in cold weather. Up here in Wisconsin one 800W string of panels I have was putting out about 750W with ambient temperatures down around 20 - 30 degrees in Feb. and March. Now that temps are up in the 80s and 90s during the day I’m lucky to see 600W peak production, even less. I have another set of panels that are rated at 1300W, a different brand, and in hot weather I’ll get about 900 - 980 W. When it was cold they’d peak at around 1,100W. So I’d say the output you’re seeing is normal.


I just hooked mine up for the first time and right now on a clear sunny day I am only seeing 30W so not sure if I’m doing something wrong or not.

Unplug it and check the voltage to make sure it is close to the rated Voc. What stage of charge % is your bluetti battery? It won’t accept a high charge rate if it is already nearly full.