The primary difference between kW (kilowatt) and kVA (kilovolt-ampere) is the power factor. kW is the unit of real power, and kVA is a unit of apparent power (or real power plus re-active power). Unless it is defined and known, the power factor is an approximate value (typically 0.8), and the kVA value will always be higher than the value for kW. About industrial and commercial generators, kW is most commonly used when referring to generators in the United States and a few other countries that use 60 Hz. The majority of the world typically uses kVa as the primary value when referencing generator sets. To expand on it a bit more, the kW rating is essentially the resulting power output a generator can supply based on an engine's horsepower. kW is figured by the horsepower rating of the engine times .746. For example, if you have a 500 horsepower engine, it has a kW rating of 373. The kilovolt-amperes (kVa) are the generator end capacity. Generator sets are usually shown with both ratings. To determine the kW and kVa ratio, the formula below is used. .8 (pf) x 625 (kVa) = 500 kW

Standby power generators are most often used in emergencies, such as during a power outage. It is ideal for applications that have another reliable continuous power source like utility power. It’s recommended usage is most often only for the duration of a power outage and regular testing and maintenance. Prime power ratings can be defined as having an “unlimited run time,” or essentially a generator that will be used as a primary power source and not just for standby or backup power. A prime power rated generator can supply power in a situation where there is no utility source, as is often the case in industrial applications like mining or oil & gas operations located in remote areas where the grid is not accessible. Continuous power is similar to prime power but has a base load rating. It can supply power continuously to a constant load but cannot handle overload conditions or work as well with variable loads. The main difference between an excellent and continuous rating is that prime power gen-sets have maximum power available at a variable load for an unlimited number of hours. They generally include a 10% or so overload capability for short durations.

Generator ends are designed to be either reconnectable or non-reconnectable. If a generator is listed as reconnectable, the voltage can be changed. Consequently, if it is non-reconnectable, the voltage is not changeable. 12-lead reconnectable generator ends can be switched between three and single-phase voltages; however, keep in mind that a voltage change from three-phase to single-phase will decrease the machine's power output. Ten lead reconnectable can be converted to three-phase voltages but not a single phase.

An automatic transfer switch (ATS) transfers power from a standard source, like a utility, to emergency power, such as a generator, when the standard source fails. An ATS senses the power interruption on the line and, in turn, signals the engine panel to start. When the standard source is restored to normal power the ATS transfers power back to the standard source and shuts the generator down. Automatic Transfer Switches are often used in high availability environments such as data centers, manufacturing plans, telecommunication networks and so forth.

Generator sets can be paralleled for either redundancy or capacity requirements. Paralleling generators allow you to join them to combine their power output electrically. Paralleling identical generators will not be problematic, but some extensive thought should go into the overall design based on your system's primary purpose. Suppose you are trying to parallel, unlike generators. In that case, the design and installation can be more complicated. It would help if you kept in mind the effects of engine configuration, generator design, and regulator design, to name a few.

In general commercial generators can be converted from 60 Hz to 50 Hz. The general rule of thumb is 60 Hz machines run at 1800 Rpm, and 50 Hz generators run at 1500 Rpm. With most generators changing the frequency will only require turning down the RPMs of the engine. In some cases, parts may have to be replaced or further modifications made. Larger machines or machines already set at low Rpm are different; they should be evaluated on a case by case basis. We prefer to have our experienced technicians look at each generator in detail to determine the feasibility and what all will be required.

Getting a generator that can handle all your power generation needs is one of the most critical aspects of the purchasing decision. Whether you are interested in prime or standby power, if your new generator can't meet your specific requirements, it simply won't be doing any good because it can put undue stress on the unit and even damage some of the devices connected to it. Determining exactly what size of generator to get is often very difficult and involves several factors and considerations.