The inverter I've selected spec's at 90%-93%, I'm thinking it's likely around 85 to 90% depending on load.
I headed a Power Systems group for a major defense contractor. Retired in 1995. We dealt with anywhere from 200 watt to 10,000 watt converters. The holy grail in converters/inverters was the efficiency number. So of course the best numbers were always in the brochures.
The best number I ever measured in a lab was about 85% at a ideal line and load condition. That was over 10 years ago.
Since you are converting directly from DC to AC those numbers may hold up. We were always going from 60 hz AC to 400 hz AC and visa versa which produced an extra loss component.