Well I think I have had 5 or 6 people present me a plan to put a solar panel system on my roof and all of then failed to say they can provide power when the supplier- Com Ed goes out. Picture a sunny day when the utility takes the power down and you have paid $25,000 to $40,000 to have solar panels put on the roof. Do you think you will have some power in your house? All but one installer say NO. The one that did say yes later called and said they can not provide the Tesla battery that is needed. Makes me want to ask them all why are you even trying to sell this system? I am a BSEE so in electronics they will not be able to trick me. So these grid tie systems are suppose to shut down when the Com Ed power goes out- did they never hear of disconnects? I get the impression that until Elon Musk sets up a Solar system to sell nationally that none of these system will be done right.
There is no reason that these systems that they sell you should not be able to generate power when power goes out in the day. Those that do not are simply not technically qualified to be selling these system. Yes, I talked to their engineers too. At night that all depends on your system and storage method. The Tesla Power wall should be able to provide minimum power during this time that was stored from the solar collection that was done during the day.
As an experiment I hooked up some cracked 6″ cells to make a 3 volt system. I think it went a little higher in full sun and it was lighting a lamp called a PR2 that is typically found in a pen light flashlight. The lamp stayed on even when cloud cover happened cutting off all the sun. You would have to cover the panels to total darkness for them to put out zero output. Now these cells I bought were chipped and missing corners but were the 8 Amp types. I think Solar is a possibility in Illinois if it is done right but Modernize does not have the contractors that really know what they are doing or at least they have not sent them to me as of yet. I guess I will have to wait for the real people to come around to put a Tesla roof on and in about 4 years that might just about be right. I should have a Telsa car by then.