Reciprocating Engines

Imagine a machine that generates power the same fundamental way a car engine does, pistons moving up and down inside cylinders as fuel ignites in a repeating stroke cycle, just scaled up enormously and running continuously on natural gas or diesel rather than intermittently on petrol. A reciprocating engine is exactly this, a proven, modular, piston-based generator, historically used mainly for backup and emergency power, overlapping with the high-HP gensets covered elsewhere on this site, but increasingly specified today for primary, continuous power at data centres.

The appeal for a data centre developer is speed and modularity, reciprocating engines can be deployed faster than the gas turbines covered elsewhere on this site, and a campus can scale its on-site power by simply adding another engine unit rather than committing to one very large single turbine, a genuinely useful property when a campus's power needs may grow in stages rather than all at once.

Wärtsilä has moved aggressively into this space, delivering a 507 MW order across 27 engines and separately debuting a 412 MW project in the United States in 2026, both described as marking reciprocating gas engines' move from standby duty into primary, behind-the-meter power rather than pure emergency backup, and Caterpillar, Wärtsilä and INNIO Jenbacher together account for roughly 18.3 GW of announced data centre capacity using this technology.

Supply has tightened here too, Caterpillar's backlog has grown more than 3.5 times since early 2024, and new large reciprocating engine orders are now landing as late as 2027 or 2028 despite manufacturing capacity roughly doubling, while in India, Kirloskar Oil Engines' 96-unit, 192 MW hyperscale order from HyperNext, also referenced under high-HP gensets elsewhere on this site, illustrates exactly how blurred the line between "backup genset" and "primary power engine" has become, purely because of data centre demand.