Jenbacher J624
Two-stage turbocharged V24 rated 4,499 kW at 47.0% electrical efficiency, the 2026 data center volume unit
Jenbacher J624 is one of 23 gas engines tracked in the SecondWatt catalogue, each with specifications, lead times and indicative secondary-market pricing.
Jenbacher J624 specs: 4,499 kW at 47.0% electrical efficiency, 60 Hz, NOx basis, overhaul intervals and the absence of a public resale price.
The Jenbacher J624 is a two-stage turbocharged V24 lean-burn gas engine rated up to 4,499 kW at 60 Hz as a generator set, at electrical efficiency up to 47.0%. That is the highest published electrical efficiency in the Type 6 family and corresponds to about 7,260 Btu/kWh on a lower heating value basis, computed as 3,412.14 divided by 0.470. INNIO rates it on DIN ISO 3046 continuous at generator terminals with a plus 5% tolerance. That rating basis is not the ISO 8528 standby basis used for diesel standby sets, and the two numbers are not comparable. Data centers made this the volume engine of 2026. INNIO booked roughly 1.1 GW of J624 capacity in July 2026 for one undisclosed US developer, more than 200 engines, described as entirely behind-the-meter prime power. A separate 1.5 GW VoltaGrid order in February 2026 covered about 300 J624 and J620 engines in 25 MW packages for delivery by 2028. The engine ships as a bare generator set, a CHP module, or containerised, and the ratings move between forms: 4,499 kW at 47.0% as a genset against 4,477 kW at 46.8% as a CHP module. Package form is part of the rating, not packaging. The J624 was added to the Type 6 platform in 2007.
Why it matters
At 47.0% electrical efficiency the J624 posts the best published heat rate in the Type 6 family, about 7,260 Btu/kWh LHV. Across two orders in six months INNIO booked about 2.6 GW of US behind-the-meter data center capacity with this engine at the centre of both. Efficiency compounds on a unit running continuously rather than a few hours a year, which is the duty these orders describe.
Who buys it
Behind-the-meter power providers and data center developers assembling 25 MW blocks, which is where the 2026 order book sits. Also combined heat and power hosts with a year-round thermal load, district energy schemes, and utilities buying dispatchable gas capacity. Buyers who want the highest published electrical efficiency in the 2 to 5 MW reciprocating class and can supply pipeline-quality gas.
Role in the data center
Behind-the-meter prime power. Both 2026 orders are explicitly prime rather than standby: the 1.1 GW award is described as entirely behind-the-meter prime power generation, and the VoltaGrid units deliver prime, backup and peaking from one system in 25 MW packages. This is the opposite duty cycle to a standby diesel set.
Key specifications
| Electrical output, 60 Hz genset | up to 4,499 kW |
|---|---|
| Electrical output, 60 Hz CHP module | up to 4,477 kW |
| Rating basis | DIN ISO 3046 continuous at generator terminals, +5% tolerance standard |
| Electrical efficiency, genset | up to 47.0 % |
| Electrical efficiency, CHP module | up to 46.8 % |
| Heat rate (computed) | about 7,260 Btu/kWh LHV |
| Thermal output | up to 4,706 kW |
| Cylinder configuration | V24, two-stage turbocharged cylinders |
| Genset dimensions | 12,800 x 2,500 x 3,100 mm |
| Published NOx basis | 250 and 500 mg/Nm3 at 5% O2, dry mg/Nm3 |
| NOx converted to US reference | 45.2 and 90.4 ppmvd at 15% O2 |
| NSPS JJJJ NOx ceiling | 1.0 g/HP-hr, or 82 ppmvd at 15% O2 |
| Major overhaul interval | up to 60,000 operating hours |
| Intermediate overhaul | 30,000 operating hours |
| Introduced to Type 6 platform | 2007 year |
| Production site | Jenbach, Tyrol, Austria (no North American assembly) location |
Technical summary
Electrical output: up to 4,499 kW at 60 Hz, generator set, DIN ISO 3046 continuous at generator terminals. CHP module rating: up to 4,477 kW at 46.8% electrical efficiency. Electrical efficiency: up to 47.0% (generator set, 60 Hz). Heat rate: about 7,260 Btu/kWh LHV, computed as 3,412.14 / 0.470. Thermal output: up to 4,706 kW. Configuration: V24-cylinder, two-stage turbocharged. Genset dimensions: 12,800 x 2,500 x 3,100 mm. Container dimensions: 12,000-20,500 x 3,000-6,000 x 3,800-15,000 mm. Published NOx basis: 250 and 500 mg/Nm3 at 5% O2, dry. Major overhaul: up to 60,000 operating hours (Clarke Energy, distributor figure). Frequency: 50 Hz and 60 Hz both offered; 60 Hz figures shown here.
Configurations and options
SCR and oxidation catalyst are catalogued options. INNIO publishes no outlet NOx figure for its SCR option as of 31 August 2026. DOE's class figure for SCR is 90-95% NOx reduction at a cost of 0.25 cents/kWh on non-fuel O&M. Hydrogen status, shipping versus announced: INNIO markets Jenbacher engines as Ready for H2, and in April 2026 demonstrated 100% hydrogen operation at 3 MW with the Net Zero Innovation Hub for Data Centers. That was a demonstration, not a shipment. Clarke Energy, an authorised distributor, describes 100% hydrogen as a future conversion whose cost and timeline require individual clarification. No catalogued hydrogen model, commercial availability date or derate figure is published, and this model's own specification block states no hydrogen capability.
Compatibility and dependencies
Pipeline natural gas figures are the ones quoted here; biogas, coal mine gas and associated petroleum gas carry different ratings. A CHP module or container build also needs a thermal host to reach its published total efficiency.
Pricing and availability
Comparable secondary-market band: 2000–3150 $ per kW installed. Trend: rising Direction is up, on demand rather than on observed transactions. INNIO booked about 2.6 GW of US behind-the-meter data center capacity in six months of 2026 and Wartsila announced a 140 million euro capacity expansion, so factory slots are the scarce good. In this category the hour meter sets used price, not the build year: an engine near its 60,000 hour major is worth materially less than an older unit fresh from one. Lead time, new: INNIO publishes no unit lead time. The 1.1 GW order of more than 200 engines booked in Q2 2026 is delivered in phases described as giving multi-year revenue visibility, and the 1.5 GW VoltaGrid order placed in February 2026 delivers by 2028. Those are programme schedules, not a single-unit quote..
Lifecycle and maintenance
Clarke Energy, an authorised INNIO distributor, puts Type 6 major overhaul at up to 60,000 operating hours. RS Motor, an independent service house, describes Type 6 overhauls at 30,000 and 60,000 hours renewing pistons, main bearings and cylinder liners, with oil filter service every 1,000 to 2,000 hours and intermediate maintenance every 10,000 hours. Both are distributor or independent figures rather than INNIO-published ones. DOE gives a 92% minimum availability for reciprocating engines as a class, and non-fuel O&M of 1.3 cents/kWh at 4.5 MW. On a continuous-duty unit the hour meter, not the build year, sets residual value.
Thermal and emissions profile
INNIO publishes J624 performance against two NOx bases: 250 and 500 mg/Nm3 at 5% O2, dry. Converting with 22.414/46 for NO2 and the oxygen correction 5.9/15.9 gives 45.2 and 90.4 ppmvd at 15% O2. 40 CFR 60 Subpart JJJJ caps lean-burn natural gas engines at or above 500 HP at 1.0 g/HP-hr NOx, which is 82 ppmvd at 15% O2, with CO at 2.0 and VOC at 0.7 g/HP-hr. The low-NOx tune clears that natively at 55% of the limit, while the 500 mg/Nm3 tune sits 10.2% above it and needs SCR. Subpart JJJJ excludes formaldehyde from VOC and sets no formaldehyde limit, so NESHAP RICE Subpart ZZZZ governs it. Non-attainment New Source Review or a LAER determination forces SCR regardless of tune, and DOE prices that at 0.25 cents/kWh on non-fuel O&M.
Common failure points
- Pistons, liners and main bearings — Rising blow-by and oil consumption as the 30,000 hour intermediate approaches
- Two-stage turbocharger — Output short of the 4,499 kW rating, especially at high ambient
- Ignition system, plugs and coils — Misfire and measured efficiency below 47.0%
- Gas train and fuel quality — Detonation, knock retard and unplanned derate
- SCR catalyst and urea dosing — NOx creeping toward the 82 ppmvd permit ceiling
- Alternator and excitation — Voltage instability under the step loads a data center imposes
Inspection checklist
Hours since major overhaul: Type 6 majors land at up to 60,000 operating hours and a unit inside 10,000 hours of one carries a large deferred cost. Hours since top-end work: the 30,000 hour intermediate renews pistons, main bearings and cylinder liners. Intermediate maintenance log: the 10,000 hour service should appear at every interval without gaps. Oil and oil filter history: service falls due about every 1,000 to 2,000 running hours. Oil analysis trend: pull the last 5 samples for wear metals, viscosity and total base number. Compression and blow-by across all 24 cylinders: one weak bank on a V24 hides inside an average. Two-stage turbocharger condition: the J624 is the only two-stage unit in the Type 6 family and no J612 or J616 rebuild quote applies to it. Aftercooler and intercooler fouling: two-stage charging puts 2 coolers in series ahead of the intake.
Procurement channels
New units go through INNIO Jenbacher North America LLC, Houston, and its authorised distributors Clarke Energy, Enerflex, Northeast Energy Systems and Western Energy Systems. There is no North American assembly. The lead production site is Jenbach, Tyrol, Austria, so every unit sold into a US project is an import, against an order book already carrying about 2.6 GW of committed data center capacity through 2028. Treat freight, customs and tariff exposure as live line items.
Regional notes
All five Jenbacher engine types appear on the North American site with 60 Hz ratings. Installed base across the US and Canada is more than 1,000 engines and over 1.7 GW, with five warehouses serving Canada and the northern US.