Will the April 8 eclipse over much of the US have an appreciable effect on the amount of solar power created while it's dark?

No. Cloud cover has a bigger affect than the eclipse.
There is also no negative harm from it. The light during a solar eclipse isn’t that different from the amount of light emitted during a regular day. So, no reason to worry – there’s no extra risk to your devices because of the eclipse

I’ve only ever seen 1 total eclipse that came directly over where I was. I waited excitedly wondering what might happen. Boy was I disappointed because everything happened so fast. It was almost over before it began. The amount of time for total darkness was less than 15 minutes. Before & after it was more of a red haze for 10–15 minutes each. There was bright sunlight on either side. I don’t think it’s going to affect any solar powered items noticeably!!!

So many people will take pictures and videos, that the flashes will make up the difference.

I hope nobody takes flash pictures. That’s just silly

^^ kinda negates the event, huh!

No. They have the energy stored in giant batteries. Probably days worth of energy.

@smudges No, it’s just stupid. You can’t flash picture the moon.

Eclipse? Of the heart?

^^ What happens? Too far away? Light doesn’t reach it to illuminate it? – obviously, but I’m just wondering what you’re thinking.

The longest total solar eclipse of the 21st century took place on July 22, 2009, when totality lasted 6 minutes and 39 seconds!

The answer to the question, though, is yes. There will be a measurable decrease of solar production during the eclipse. It won’t be that significant though. It will be interesting to look at solar production graphs during it.

@Caravanfan thanks, I sort of figured that. It would be interesting to see the actual numbers.

The rate (kW) will drop down to almost zero during the darkest part of the eclipse but the total energy for the day (kWh) will not be affected much because the main eclipse will only be for a few minutes. Notice the h (hours) in the units.

Last October, during the annular eclipse in the West, there was a notable drop in energy production from panels along the arc from Oregon to New Mexico.

Of particular note for those of us out watching it was the temperature drop during the peak of the eclipse, about 15 degrees Fahrenheit from before the eclipse started.

Doubtful.

No more than cloudy days.