An 18 KW in natural gas is just like a 20 KW in propane. Actually, natural gas is not as powerful as propane. Propane is more muscular. If you have a 20 KW in propane, it will remain 20 Kilowatt. In natural gas, 500kw Diesel Generator it drops to 18 KW. It drops 2 KW. Some manufacturers have allowed for that drop and not much. Functional indeed saying anything about of which. They won't talk about doing it. They are not letting it known to your public or through their dealers or manufacturers. Simply say that it can be capable insects same. It's not at all the pretty same. The fuel burns differently. Propane burns hotter than natural gas so therefore it gives the engine less horsepower so therefore it's got less Kilowatt.
Here could be the thing.