Prime Power
There are many differences between PRIME power and STANDBY power the following are but a few of them.

A prime power generator must be capable of running flawlessly for many hours running up to 7/24-365.

Because of their higher running hours, a prime power generator must run economically. It is also important that should something go wrong, parts are readily, locally and quickly available. Prime rated gensets should have therefore have established service and parts networks so that warranty work can be done close to your location and parts can come from local parts networks.

Power generation is a high torque application for an engine. All generators consume oil. Prime rated generators tend to have larger lubricating oil reservoirs.

Backup rated generators, because usage is intermittent have higher performance ratings, higher by at about 10% to 15%. While many generators are rated for both prime and backup there are also less expensive generators available rated only for backup.

If your application has the generator running for longer periods of time consider co-generation. An amazing amount of heat can be harvested and put to profitable use when you run your generator.

Examples of co-generation:

Farmers, and saw mills can use the heat from their generators to pre-heat air for driers.

Camps and campgrounds can heat their shower water and kitchen hot water supply.
Homes, cottages, camps and industry can use this heat to heat their facilities.
Factories use the heat for water and area heating.
Why purchase expensive diesel fuel and then dissipate 70% of BTU into the environment?