Charlie100

A reputable inverter  from a reputable company no problems that I can see. So long as the various bits of extra kit SPDs disconnects change over switch  etc are installed the extras are not excessive. Kudos to your mate on checking on pricing. The rest of us ploughed ahead and then toted up the final figure. 

As long as he uses most power during the day, it will definitely lower costs.
3Kwp will make around 15kwh a day, so he'll be offsetting just over half his consumption, again, if over half his consumption is in the middle of the day.
I don't know the Solis inverters, but they are on the Cape Town approved list so they do tick at least some boxes. Friend of mine who is from the UK seems to know them well.
I'd say 15k should be enough for the install. @Chris Hobson or @SilverNodashi are more hands-on with that.
I'm a big Fronius fan, or perhaps even SMA, but that's going to cost a good 70% extra. I don't know what the warranty is like on the Solis, I do know it is very good on the European spec inverters. Depending on that install fee, maybe you can squeeze a higher-end inverter :-)

It's illegal to spin it back, the council will see that as meter tampering. But if there is a grid limiter involved (as Noobie says) he should be fine, at least no electronic nannies to disconnect you for the odd pushback when a large load switches off.