There is so much wrong with this concept that I don't know where to start. I am in the solar industry and I want to try and explain why this is a really dangerous thing to do. First I will say that It will absolutely work and for somebody that that understands what they are doing and that knows how their receptacles are wired and what circuits they are on. OK.. hopefully I can explain why I think this is a dangerous concept.
A 120V receptacle is normally on a 15 AMP breaker.
There are usually multiple receptacles on a circuit. The circuit breaker and the wire for that circuit are usually designed for 15AMPS.
NOW, lets plug in a 10 AMP load on that circuit... AND inject another 5 AMPS from the solar array that you just plugged into that circuit...
what is going to happen?
The 5 amps of solar will serve that 10 AMP load and an additional 5 AMPS will flow from the main load center through the circuit breaker to service the load. FANTASTIC you are only buying 5 AMPS instead of 10. All is good in the world!
NOW, what if somebody plugs in more loads to that circuit. lets say that now you have 18 AMPS of total load on that circuit with the same 5 AMPS of solar being injected.
Without the solar the breaker would trip but because the 18 AMPS would have exceeded the 15 amp breaker limit.
BUT now you are not pulling 18 AMPS through the breaker you are only pulling 13 AMPS through the breaker BUT you are injecting an additional 5 AMPS of solar into that circuit.
you are now potentially OVERLOADING the wire. (depending on which receptacles the loads are on and where the solar is back feeding into the circuit)
That wire is going to start getting hot and you now have a very, very dangerous situation.
The circuit is overloaded but the breaker has not closed because the breaker isn't overloaded.
I hope that makes sense... Hire a NABCEP certified electrician and use the proper backfeed breakers to feed your solar into your service panel safely! Stop worrying about if you need a permit or not, THERE IS A REASON FOR ELECTRICAL CODES AND PERMITS, it's not some conspiracy to make you pay for something, its an effort to keep homeowners safe and to help them not get ripped off by stupid ideas like this one!