Solar Turbines Centaur 50

4,600 kWe ISO generator set on the same shared skid as the Centaur 40 and Taurus 60

Solar Turbines Centaur 50 is one of 21 gas turbines tracked in the SecondWatt catalogue, each with specifications, lead times and indicative secondary-market pricing.

Solar Turbines Centaur 50 gas turbine: 4,600 kWe rating, ambient derate data, SoLoNOx emissions profile, and verified used pricing from about 58 dollars per kW.

The Centaur 50 is Solar Turbines' next step up from the Centaur 40: a single-shaft industrial gas turbine, main reduction gearbox, and synchronous generator with a permanent-magnet exciter, built onto one skid-mounted enclosure and rated 4,600 kWe ISO base load at 11,630 Btu/kWe-hr and 29.3% thermal efficiency. It shares its common engine skid with the Centaur 40 and Taurus 60, and the OEM's own ambient-temperature derate curve shows output swinging from roughly 5,100 kWe at -30C down to roughly 4,200 kWe at +45C, a spread on the order of 21% from cold to hot extremes. Used-market listings surface at least three legacy nameplates converging on this same power class: T4501 on rebuilt 4,000 kW units, Type H / GSI-CH-ID on 1986-built 4,000 kW units, and EH-5701-59 on rebuilt 3,800 kW units, all sold as "Centaur 50" without a published OEM crosswalk connecting the designations. One T4501 listing states outright "Not SoloNox," a real flag that a meaningful share of the used fleet predates Solar's 1992 SoLoNOx rollout. A real California BACT permit for this model, using water injection plus SCR rather than SoLoNOx, runs 9 ppmvd NOx permitted and 4.2 ppmvd achieved, against a federal floor of 42 ppm for this size class. No overhaul interval in fired hours was sourced for this model; field-observed hours since rebuild ranged from roughly 3,000 to over 40,000 across used units.

Why it matters

The published ambient-temperature derate curve is the number a hot-climate buyer needs before sizing a site around the 4,600 kWe ISO nameplate: output falls to roughly 4,200 kWe at +45C, on the order of a 21% swing from the cold-ambient end of the curve.

Who buys it

Oil and gas operators, industrial cogeneration sites, and data center developers who need more output than a Centaur 40 but cannot wait on a Taurus- or Mars-class order buy the Centaur 50 for its combination of a proven, well-parted small frame and above-average used-market depth relative to larger Solar packages. It is a common step-up choice for a buyer already standardizing on the shared Centaur/Taurus 60 skid family.

Key specifications

Technical summary

ISO base-load electrical output: 4,600 kWe Heat rate: 11,630 Btu/kWe-hr (12,270 kJ/kWe-hr) Thermal efficiency: 29.3% Pressure ratio: 10.6:1 Exhaust flow / temperature: 151,410 lb/hr (68,680 kg/hr) at 950F (510C) Ambient derate: approximately 5,100 kWe at -30C to approximately 4,200 kWe at +45C 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: 83,300 lb (37,785 kg) / 10'5" (3.2 m) Legacy nameplates in the used fleet: T4501, Type H / GSI-CH-ID, EH-5701-59

Compatibility and dependencies

The Centaur 50 generator set shares its common engine skid and 1500/1800 rpm reduction-gearbox family with the Centaur 40 and Taurus 60, per Solar's own product page and confirmed by EthosEnergy's service scope for the three models together. Package height is identical, 3.2 m / 10'5", across Centaur 40 and Centaur 50, which broadens shared-component parts availability but not turbine hot-section parts, which do not cross over between the two ratings.

Pricing and availability

Published price range: $250,000 - $2,700,000. Trend: flat No time-series data exists in the sources checked, so a directional trend cannot be established, and price_trend is set to flat as a neutral default pending more observations over time. Lead time, used or refurbished: Not established from sourced listings; the new/crated unit found was offered as immediately available, unused inventory..

Lifecycle and maintenance

Field evidence shows a wide range of hours-since-rebuild across the used fleet, from roughly 3,000 package hours on a 1986-built unit to over 40,000 hours since a 2007 rebuild, suggesting these engines run well past 40,000 hours between major work under Solar's program. Against a used-market price as low as $250,000, an overhaul in the low-to-mid six figures would consume a far larger share of asset value on a machine this size than the same dollar overhaul on a 15 MW-plus frame.

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 — 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 and PMG exciter — falling insulation-resistance trend or hot spots on thermal scan
• Water injection system on non-SoLoNOx units — nozzle plugging or inconsistent NOx control during operation
• Control console and Turbotronic electronics — obsolete card sets or no vendor firmware support on pre-2005 consoles
• Enclosure and inlet/exhaust ductwork — corrosion or acoustic panel degradation on outdoor-stored units

Inspection checklist

Total fired hours since new — used units ranged from roughly 3,000 to over 40,000 hours since a rebuild, so ask for the actual number Fired hours since the last hot section inspection — request the logged figure, not a verbal estimate Total starts logged — one field listing showed 1,500 starts against 26,000 total hours, a meaningfully cyclic duty profile Borescope images dated within the last 12 months — request the photo set itself, not a summary write-up Combustion system type in writing — confirm SoLoNOx versus conventional; a "Not SoloNox" tag on a listing is a real permitting flag SoLoNOx conversion date if retrofitted — factory SoLoNOx was not standard across the line until 1992 Water injection or SCR hardware present — a non-SoLoNOx unit needs one of these to approach the 9 ppm NOx figure a SoLoNOx combustor meets on its own Exciter and generator winding insulation resistance — a dated megohm reading, not a pass/fail claim alone Generator bearing vibration trend over the last 12 months — a trend line, not a single snapshot reading Main reduction gearbox oil analysis — shared design across Centaur 40, Centaur 50, and Taurus 60 Fuel nozzle condition on the annular combustor — check for coking or erosion during the borescope pass Control system generation — pre-2005 consoles predate Solar's InSight remote-diagnostics platform Enclosure and skid corrosion — package weighs 83,300 lb; outdoor or coastal storage accelerates this Number of prior installation sites and total starts — a relocated, heavily-cycled package carries more requalification risk Nameplate cross-check against legacy designations — Centaur 50, T4501, Type H/GSI-CH-ID, and EH-5701-59 tags describe overlapping hardware with different parts and emissions eligibility

Procurement channels

Several dealers listed the same legacy-nameplate hardware (Type H, T4501) under different names, underscoring that a buyer needs to search multiple designations, not just Centaur 50, to see the full available inventory.

Regional notes

Sourced examples include a Caltech campus installation in California, a St. Croix, U.S.