According to these 2 links, its around 3.5HP required to run, which still isn't terrible.
https://www.zena.net/htdocs/alternators/alt_inf2.shtml
https://www.thecalculatorsite.com/conversions/common/watts-amps.php
600w @ 12v is 50amp. Divide by their 15, and I got 3.5HP (ish).