To be fair, I've rarely seen a 4kWp system that hasn't been calculated to perform better on a 4000TL than a SB3300. The 4000TL is oversized, without a doubt, but it is just that bit more efficient. Hopefully when the 3600TL comes out it will be THE inverter for 4kWp systems. Currently, we tend to use a lot of Fronius IG TL 36 inverters. For often than not, they offer the best results.