There is no marketing department involved in converting hp to kw. These are simply two different units of power, and the exact conversion ratio can be found in any technical manual or on internet sites. 52 hp is 38.7 kw, and so with a rule of thumb of allowing 20% losses, the net output is 30.96, still more than the 30 kw rating. I'd certainly agree that no one should run a 30 kw standby generator at the rated load for any long period of time. Starting loads on electric motors or other devices can be much higher than running load, and so the size should be chosen with a substantial reserve in mind. The average running load factor was in the 25-30% range.