The reason most inverter manufacturers advise against this is that the closer the start up voltage is to the operating voltage the more likely the inverter is to keep switching on and off in marginal conditions. This can cause premature wear of components.
96% max efficiency, 96.5% for their 3kW model, as far as I can see from the spec. I think the Aurora's are 96.8% (not sure though) so not quite as efficient, no, but they aren't transformerless so those figures are not too shabby I think. They do seem to have some nice features as standard though, and are designed with installers in mind. How to Install an EnaSolar Grid Tied Solar Inverter - YouTube
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