Technology
A reciprocating engine generator is a large piston engine driving an alternator, delivered as a package of a few megawatts and paralleled with others to reach the output required. It is less efficient than a large turbine and it can be on site and running in a fraction of the time.
In one sentence
A reciprocating engine generator uses a piston engine — diesel, natural gas or dual-fuel — to drive an alternator, supplied in modular units of a few megawatts that are paralleled to reach the required output.
The engineering case is modularity. Ten engines of five megawatts reach the same output as one turbine, but they arrive on trucks, they are commissioned in sequence, one can be serviced without taking the plant off line, and the plant holds its efficiency at part load where a single large machine would not. Start-up is fast enough to matter: an engine reaches full output in minutes, and in the standby case in seconds.
The supplier base is also much wider than the turbine market, with several manufacturers in every size class and lead times measured in months rather than years. That combination — quick to buy, quick to install, quick to start — is why generation installed to carry a campus while its grid connection is completed is usually engine plant, and why the turbine conversation and the engine conversation have different timescales.
Availability is the argument. With units in parallel, losing one costs a fraction of output rather than all of it, maintenance happens on a rotating schedule without an outage, and the plant can be grown in steps as load arrives. The penalty is more equipment to install, more auxiliaries, and a larger footprint per megawatt than a turbine of the same rating.
Engine exhaust carries nitrogen oxides and particulates at levels that permits in most jurisdictions will not accept untreated. Selective catalytic reduction with urea dosing, oxidation catalysts and particulate filters are therefore part of the plant rather than an option, and they add capital, footprint, a consumable and a maintenance regime that the engine itself does not need.
Continuous plant is usually spark-ignited gas, which is cleaner and cheaper to run where a firm gas connection exists. Diesel dominates where the machine must start on stored fuel with no external supply, which is the standby case. The two share manufacturers and very little else about how they are specified, permitted and operated.
2 of these are marked as a chokepoint: a handful of qualified suppliers, a multi-year lead time, or a single geography.
Engines in parallel need synchronising and protection equipment, and the medium-voltage side of it is on the same extended lead times as everything else electrical.
TransformersCrankshafts, blocks and heads are heavy machined parts, and the capacity to finish them is the practical limit on how quickly production rates rise.
Bearings and precision machiningWhat the permit allows determines the catalyst system, the urea supply and in several regions whether the plant can run continuously at all.
Gas plant needs a firm connection; diesel plant needs tankage, a delivery contract and fuel that is polished and rotated before it degrades.
Engines are maintained on running hours, and a plant of a dozen units consumes a service programme that regional dealer networks have to be able to staff.
Other pages in this map that name Reciprocating engines as something they cannot do without.
What each company supplies at this step, and — where a public figure exists — its share of this specific market — with what that share measures, the period it covers and who published it. Some rows also show the company’s own reported revenue for the segment covering this step, which is a different thing: it says how much this business matters to that company, not how much of the market it holds. Not a ranking and not a recommendation.
Supplies diesel and gas engine generation across the range used for bridge and standby plant.
Power & Energy segment — -4.6% of Caterpillar’s reported revenue (-$5.1B)FY2025 · company filings · not a market share
Supplies engine generation and the associated controls and paralleling equipment.
Power Systems segment — 22.2% of Cummins’s reported revenue ($7.5B)FY2025 · company filings · not a market share
Supplies the high-speed diesel and gas sets sold under mtu, between engine-scale and turbine-scale plant.
Supplies medium-speed engine plant designed for continuous and flexible generation rather than standby.
Supplies the gas engine range used for continuous on-site generation, sold under Jenbacher.
Supplies large medium-speed engine plant for power generation, at the top of the reciprocating range.
Supplies packaged generation at the smaller end and is moving upward into data-centre set sizes.
Supplies packaged engine generator sets and the switchgear sold with them.
Whether engine plant keeps its lead-time advantage over turbines as both order books lengthen.
Whether continuous-duty permits for gas engine plant become harder to obtain in load-growth regions.
Whether operators retain bridge engine plant as standby capacity once grid connections arrive.
Each page explains one technology in plain language, states what it depends on, and names companies by what they supply at that step. Company roles are described qualitatively and deliberately carry no market shares, revenue figures or rankings — those change faster than an explainer can, and a stale number is worse than none. Ticker links point at company pages on this site and are provided for reference only.
Nothing here is investment advice, a recommendation, or a forecast. A company named on a page about a technology is not thereby a good investment, and the chokepoints described are structural facts about supply chains rather than predictions about prices. Technology moves; where a page describes something as unresolved or in development, that was true when it was written.