Reciprocating Gas & Diesel Gensets

A reciprocating generator set — a genset — is a piston engine coupled to an alternator. It burns fuel in cylinders to turn a crankshaft, the same principle as a car or truck engine, scaled up to generate electricity, typically around 1 to 3 MW per set.

Reciprocating engines are not turbines, and the difference is the whole point:

• Fast start and load-following — a genset can start and take full load in seconds, and follow a swinging load efficiently, making it ideal for standby and backup.
• High part-load efficiency — piston engines hold their efficiency down at partial load better than a small turbine, which matters when a set rarely runs flat out.
• Modular scaling — capacity is added by paralleling more sets, so a plant grows in small, redundant increments.

That combination is why gensets dominate backup and mission-critical power, including the emergency and continuous power behind data centers. For a direct comparison with turbines in that setting, see gas turbine vs reciprocating engine for data centers.

Reciprocating gensets run on two main fuels, and the choice shapes the use case:

• Diesel — the standard for standby and emergency power. Diesel sets are energy-dense, fast to start, and simple to fuel from on-site tanks, which makes them the default for backup where a set may sit idle for long periods and then must carry load instantly. The Cummins QSK and QST lines are diesel.
• Natural gas — favored where a gas supply is available and the set runs more hours, for lower fuel cost and lower emissions, and for prime or continuous duty rather than pure standby. The Cummins HSK78G is a natural-gas set.

Many sites run diesel for guaranteed emergency backup and gas for prime or continuous generation, matching each fuel to the duty it does best.

A genset carries a power rating tied to how it will be run — the same physical set is rated differently for different duties, so the rating matters as much as the engine:

• Standby — maximum power for the duration of a utility outage, with no sustained overload capability. The highest nameplate number, for emergency backup that runs occasionally.
• Prime — unlimited running hours at a variable load, with overload capability. For sites that run off-grid or as a primary source.
• Continuous — a constant load for unlimited hours. The most conservative rating, for baseload duty.
• Data-center / mission-critical — a rating class for the continuous, high-availability duty a data center demands. See data-center-rated generator sets.

Because the rating changes the usable output, a genset's "size" is only meaningful alongside its duty rating — which is confirmed at quote.

The reciprocating gensets available through Pantheon are below, largest first. Per-unit output and fuel are shown on each tile; exact rating (standby / prime / continuous) and configuration are confirmed at quote. The Cummins QSK diesel line anchors the range — the ~3 MW QSK95 down through the QST30 and KTA50 — alongside the natural-gas HSK78G. Each links to its full specification.

Reciprocating gensets are quoted per configuration on request — the figure depends on the model, fuel (diesel or gas), duty rating (standby, prime, or continuous), enclosure and emissions package, and quantity, all confirmed at quote. Tell us the power band, fuel, and duty you are planning around and we will return availability and a facility-fit review.

Browse the full gensets catalog to compare models, read about data-center-rated generator sets for mission-critical duty, or compare gensets with turbines in gas turbine vs reciprocating engine for data centers.

Figures on this page are representative public manufacturer specifications for the reciprocating-genset class and the models shown — not a specification of any specific unit. Actual output, rating, condition, and configuration vary by unit and are confirmed at quote; nothing here is an offer, a price, or a warranty.