Solar Turbines Centaur 40
Solar Turbines Centaur 40 generator set, 3,515 kWe ISO base load
This model is part of SecondWatt’s gas turbine research catalogue. Specifications and price observations are included where supported by sources. Equipment availability and commercial terms require confirmation.
Solar Turbines Centaur 40 gas turbine: 3,515 kWe rating, SoLoNOx emissions data, overhaul guidance, and verified used pricing from about 79 dollars per kW.
The Centaur 40 is Solar Turbines' entry-level power-generation package: a single-shaft industrial gas turbine, main reduction gearbox, and synchronous generator built onto one skid-mounted enclosure, rated 3,515 kWe ISO base load at a heat rate of 12,240 Btu/kWe-hr and 27.9% thermal efficiency. It shares its common engine skid with the Centaur 50 and Taurus 60, and both 1500 rpm (50 Hz) and 1800 rpm (60 Hz) reduction-drive outputs are offered. Both conventional and SoLoNOx (dry low-emissions) combustion are sold as factory options on current production.
The used market for this class runs deeper than for any larger Solar frame, and it runs under more names than the current catalog suggests. Nameplates including 4701, T4701, and Type H all describe engines converging on the same 3.0-3.5 MW class from earlier points in Solar's naming history, with no OEM crosswalk table connecting them to "Centaur 40." A buyer searching only the current model name can miss real inventory listed under a legacy tag.
SoLoNOx became a factory option in 1992, carrying a 9 ppm NOx warranty; a real California BACT permit for this model, with SCR added, runs 5 ppmvd NOx, while the federal NSPS floor sits at a much looser 42 ppm. Three published prices attach to this model: a $270,000 used unit near $79/kW, a clean new unit near $800/kW, and a third new-condition listing whose stated 5.6 MW rating does not match the OEM 3,515 kWe nameplate. Solar publishes no overhaul interval in fired hours for this model; the best proxy is a 32,000-fired-hour rotor life figure from a third-party overhauler.
Why it matters
This is the most numerous Solar generator set in the secondary market, which makes it the fastest to deliver, a real advantage for a data center buyer who cannot wait for a Titan or Mars slot. That depth comes with a real cost: a wide spread of legacy nameplates and pre-1992 non-SoLoNOx units means emissions compliance and parts sourcing both demand more diligence here than on a newer, single-designation model.
Who buys it
Oil and gas operators, industrial cogeneration sites, and increasingly data center developers who need power sooner than a Titan- or Mars-class order can deliver buy the Centaur 40 for its combination of low unit cost and fleet depth. A buyer priced out of larger Solar frames, or unwilling to wait on new-build lead times, can often source two or three Centaur 40 units in place of one larger machine.
Role in the data center
Bridge or prime power block of about 3.5 MW per generator-set unit, assembled in multi-unit rows feeding campus medium-voltage switchgear. Its case rests on availability and unit cost rather than efficiency: at 27.9% thermal efficiency it burns more fuel per kWh than any larger Solar frame, so it suits bridge duty on a limited run-hour budget more than multi-year prime service.
Key specifications
| ISO electrical output | 3515 kWe |
|---|---|
| Heat rate | 12,240 (12,910) Btu/kWe-hr (kJ/kWe-hr) |
| Thermal efficiency | 27.9 % |
| Pressure ratio | 10 :1 |
| Exhaust flow | 150,715 (68,365) lb/hr (kg/hr) |
| Exhaust temperature | 830 (445) F (C) |
| Gas producer turbine max speed | 14,944 / 14,951 rpm (50 Hz / 60 Hz) |
| Main reduction drive output speed | 1500 / 1800 rpm (50 Hz / 60 Hz) |
| Generator configuration | 4-pole, 3-phase, 6-wire, wye, synchronous description |
| Generator voltage, 60 Hz | 4160 / 6900 / 12,470 / 13,200 / 13,800 V |
| Generator voltage, 50 Hz | 3300 / 6600 / 11,000 V |
| Package weight | 67,150 (30,460) lb (kg) |
| Package height | 10'5" (3.2) ft-in (m) |
| Fuel types | natural gas, diesel, dual, low-Btu gas description |
| SoLoNOx emissions warranty | 9 NOx / 15 CO / 15 UHC ppm |
| California BACT limit with SCR, Saint Agnes Medical Center | 5 NOx / 50 CO / 10 NH3 ppmvd @ 15% O2 |
Technical summary
ISO base-load electrical output: 3,515 kWe. Heat rate: 12,240 Btu/kWe-hr (12,910 kJ/kWe-hr). Thermal efficiency: 27.9%. Pressure ratio: 10:1. Exhaust flow / temperature: 150,715 lb/hr (68,365 kg/hr) at 830F (445C). Combustion system: SoLoNOx (DLE) or conventional, factory option. SoLoNOx emissions warranty: 9 ppm NOx / 15 ppm CO / 15 ppm UHC. Main reduction drive output speed: 1,500 / 1,800 rpm (50 / 60 Hz). Package weight / height: 67,150 lb (30,460 kg) / 10'5" (3.2 m). Legacy nameplates in the used fleet: 4701, T4701, Type H.
Major variations
Used-market listings surface at least three legacy nameplates for engines in this same class: 4701 / 40S 4701(S), T4701 on a 1984-built 3,200 kW-nameplate unit, and mid-1980s Type H hardware described as 3.0 MW-class continuous-duty units. Solar publishes no crosswalk table tying these legacy designations to the Centaur 40 name; the connection rests on their 3.0-3.5 MW nameplate ratings and consistent broker usage rather than on an OEM document, so confirm the engine designation with Solar before purchase. A buyer searching only Centaur 40 risks missing inventory tagged 4701, T4701, or Type H that is mechanically the same engine family.
Configurations and options
Combustion is ordered as SoLoNOx, a factory option since 1992 carrying a 9 ppm NOx / 15 ppm CO / 15 ppm UHC warranty, or as a conventional combustor, and pre-1992 units carry no SoLoNOx at all. The reduction drive is built for 1,500 rpm (50 Hz) or 1,800 rpm (60 Hz) output, with generator voltage options of 4,160, 6,900, 12,470, 13,200 or 13,800 V at 60 Hz and 3,300, 6,600 or 11,000 V at 50 Hz. Fuel options are natural gas, diesel, dual-fuel, and low-Btu gas, and the annular combustor carries 10 fuel injectors.
Compatibility and dependencies
The generator-set (single-shaft) Centaur 40 is a distinct product from the Centaur 40 mechanical-drive package, which uses a two-shaft, free-power-turbine arrangement to drive a gas compressor rather than a generator, sharing only the core engine. The generator-set version shares its common engine skid and reduction-gearbox family with the Centaur 50 and Taurus 60, which broadens parts availability for the shared components but not for the turbine hot section itself.
Pricing and availability
Published price range: $270,000 - $2,800,000. Trend: stable All three published prices for this model are 2026 snapshots from different sellers, with no earlier public price series for comparison. No public price series exists for this model, so no directional trend can be established as of August 2026. Lead time, new: 36-60 months as of August 2026, per broader Solar and Caterpillar order-book conditions; confirm against Solar or an authorized distributor. Lead time, used or refurbished: Weeks; several units on offer in August 2026 were listed zero-hours-since-rebuild or immediately available. Warranty, used: As-is is the norm on broker listings, none of which published warranty terms; Solar's Pre-Owned Equipment program offers warranty reinstatement on units routed through the factory exchange channel.
Supply, delivery and overhaul
2 units listed without public prices.
- Manufacturer-wide delivery estimate: 29 months
- Factory exchange overhaul
Lifecycle and maintenance
Solar publishes no Centaur 40-specific hot section or major overhaul interval in fired hours, and no overhaul cost in dollars. The best available benchmark is a third-party rebuild specification rather than an OEM interval: EthosEnergy states 32,000 fired hours of expected rotor life after a factory-equivalent overhaul. Field evidence supports long on-condition running, with one mid-1980s unit logging over 50,000 hours before its first major overhaul in 2005. Against used-unit prices as low as 270,000 USD, a six-figure overhaul consumes a far larger share of asset value on a machine this size than the same work on a 15-30 MW frame.
Thermal and emissions profile
SoLoNOx (dry low-emissions) combustion has been a factory option since 1992, carrying a 9 ppm NOx / 15 ppm CO / 15 ppm UHC warranty on natural gas. A California BACT permit for this exact model, with SCR added on top of dry low-NOx combustion, runs 5 ppmvd NOx at 15% O2, well below that SoLoNOx-alone warranty figure. Solar's published base-load figures place the Centaur 40 in the federal small-turbine bin at 50 MMBtu/hr or less, where the NSPS floor is a much looser 42 ppm NOx at 15% O2, but the margin to that 50 MMBtu/hr line is thin, so confirm peak-load heat input on the specific unit's data sheet. A pre-1992 or legacy-nameplated (4701/T4701/Type H) unit without SoLoNOx needs its combustion type verified in writing before a buyer assumes it can be sited.
Common failure points
- Combustor liner and fuel nozzles — elevated or uneven exhaust temperature spread across cans, visible coking on borescope
- Hot gas path blades and nozzles (3-stage reaction turbine) — coating spallation, tip rub marks, or cracking visible on borescope images
- Main reduction gearbox — rising bearing temperature or metal particulates in oil analysis
- Generator windings — falling insulation-resistance trend or hot spots on thermal scan
- Control console and Turbotronic electronics — obsolete card sets or no vendor firmware support on pre-2005 consoles
- Fuel system and dual-fuel changeover hardware — sticking valves or failed changeover on units idle for years
- Enclosure and inlet/exhaust ductwork — corrosion or acoustic panel degradation on outdoor-stored units
Inspection checklist
Total fired hours since new: compare against the 32,000-hour rotor life benchmark cited by third-party overhaul shops. Fired hours since the last hot section inspection: request the logged number, not a verbal estimate. Total starts logged: each start-stop cycle drives more thermal fatigue than an hour of steady running. Borescope images dated within the last 12 months: request the actual photo set, not a summary paragraph. Combustion system type in writing: SoLoNOx trims NOx to roughly 9 ppm versus 40-plus ppm uncontrolled. SoLoNOx conversion date if retrofitted: factory SoLoNOx was not standard across the line until 1992. Turbine blade and nozzle condition across the 3-stage reaction turbine: check for coating loss or cracking. Fuel nozzle count and condition: 10 injectors on the annular combustor; check for coking or erosion.
Procurement channels
Priced and unpriced listings for this model run through Salvex (trader-to-trader auction), Machinio (multi-seller aggregator), Aaron Equipment, Reflowx, EthosEnergy (OEM-adjacent overhaul and resale), and USP&E. Machinio-aggregated prices do not always match the seller's own live inventory page, so a buyer should confirm any aggregator price directly with the seller before relying on it.
Regional notes
Published examples span a Fresno, California site permit, an Alaska-based new-unit seller, and a Houston, Texas overhaul depot, with no single region dominating. That spread is consistent with the model's fleet depth: a buyer can usually find a Centaur 40 within freight range of the site, which is not true of the larger Solar frames.
Content owner: Gary Martin, SecondWatt