Today, around noon, I washed my 30 PhotoWatt solar panels.

They were not particularly dirty - the last rainstorm was about 3 weeks ago. But I squirted the hose at 'em, then went over each one with a squeegee.

The whole time I was monitoring things with the solar Inverter Viewer. To my amazement, the solar panels' output jumped 8.5 percent compared with 30 minutes earlier. When I compare today's readings with yesterday, it's an 8.6 percent increase. Right now, three hours later, it's still 8.5 percent increase in electric output.

Again, the panels were not very dirty - I'd say a light dusting of smog. Not even any bird droppings. In the future, I'll be washing my panels more often!

And when I install a west-facing set of panels, I'll make sure there's an easy way to reach them with hose and squeegee.

you really didn't get 8% more, but merely recovered what you didn't realize what you had lost.

This is due to temperature. By putting water on the modules you cool them down which increases the efficiency and leads to an increase in output. But once you turn the water off the modules return to there original temp and efficiency. There is no way to sustain this. There has been talk on SG and other message boards about hybrid PV and Hot water panels that would take advantage of cooling the PV module but as far as I know there are no working units available to the public. There is also questions about the cost effectiveness of a hybrid PV / Hot Water panel but that would be a whole different topic.

yes, that's exactly right and my summation was pretty correct as he lost output from solar heat.

Actually i took it as the output was increased even the following day which would show dirt on the panels

he still didn't gain more than the panel was made for. it's not like for example a 100w pv that was outputting 108w, but was more like say 93w and to 101w output as the 100w pv will normally produce a bit more power when it's cooled, and it was outputting less than its capabilities when it's that dirty. it's the same pv and there really isn't any gain over what would be considered normal for the pv. his wording made it seem like he's getting 8% more than normal for that pv, but he only recovered what was the same ability of the pv that was lost due to the dirt and heating. one could put their hand over the pv then take it off and make that same kind of claim and sure it increased, but not beyond what would've been normal, for it was going from a subpar condition to normal and that increase was only what was lost to those factors.

Very true neil he just got back to the regular spot so he actually was losing 8%