Siemens Energy SGT-A05 (Rolls-Royce 501-K) Gas Turbines for Sale

Manufacturer: Siemens Energy

4.0-5.8 MWe aeroderivative, formerly the Rolls-Royce and Allison 501-K, that Siemens Energy also sells as the Via5.8 trailer unit.

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.

Siemens Energy SGT-A05 (former 501-K) gas turbine: 4.0-5.8 MWe, 60-second start, DLE 25 ppm NOx, Via5.8 single-trailer mobile unit and overhaul intervals.

Why it matters

It is a 4-6 MW block that reaches full power in 60 seconds, can black start and fits on one road trailer, so the same engine serves fixed combined heat and power and rapid-deployment duty. Siemens offers core engine exchange, an engine lease program and more than ten upgrades for the 1,720-unit fleet, including KB7S to KB7HE. Assessment: on published ISO ratings the KB7HE (5.8 MWe, 33.2%) sits close to the Solar Taurus 60 (5,670 kWe, about 31.5%), but its DLE rating is 25 ppm NOx against 15 ppm on the Taurus 60's SoLoNOx guarantee.

Who buys it

Hospitals and multi-utilities running combined heat and power (Siemens Energy cites a KB7S at Royal Aberdeen Infirmary producing 5.5 MW and 12 t/h of steam, and two KB5S units at Hera in Bologna); sites that need fast-start standby power, such as Sellafield; onshore and offshore oil and gas operators using the single-shaft version; and users of the trailer unit, which Siemens lists for remote oil, gas and mining power, temporary power for utilities, the military and construction, and critical loads such as hospitals, universities and data hubs.

Role in the data center

Siemens Energy lists data hubs among the critical-process loads for the SGT-A05 Mobile Power Unit. Assessment: at 4-6 MW per unit the engine fits bridge or temporary power while a campus waits for grid capacity, standby and black-start duty, or a combined heat and power block whose 495-560 C exhaust can drive absorption chilling. A 100 MW campus would need 18 to 25 units at ISO rating (calculated).

Key specifications

Technical summary

Siemens Energy rates the KB5S, KB7S and KB7HE at 4.0, 5.4 and 5.8 MWe gross at the generator terminals (ISO, gaseous fuel, no inlet or exhaust losses, gearbox and generator losses included), with gross efficiencies of 29.7, 32.3 and 33.2% and heat rates of 11,504, 10,570 and 10,281 Btu/kWh (12,137, 11,146 and 10,889 kJ/kWh). Pressure ratios are 10.3, 14.2 and 14.4:1, turbine speeds 14,200, 14,600 and 14,600 rpm, exhaust flows 15.4, 21.3 and 21.4 kg/s, and exhaust temperatures 560, 495 and 520 C on the product page (508 C for the KB7HE in the 2021 brochure). DLE NOx is 25 ppmvd or less at 15% O2 on gas fuel. Full power comes within 60 seconds. The power-generation package weighs about 35,000 kg and measures 9 x 2.7 x 3.1 m without the inlet filter house and stack. The Via5.8 mobile unit delivers up to 5.8 MWe from a trailer 53 ft long and about 105,000 lb without a tractor.

Major variations

Siemens Energy's current offering is the KB5S, KB7S and KB7HE, all for 50 or 60 Hz. The KB5S (4 MW class) is a single-shaft, cold-end-drive engine. The KB7S (5 MW class) adds a single-stage boost compressor, improved vane cooling and higher-strength turbine blades. The KB7HE adds a High Efficiency Compressor upgrade to the KB7S for 8% more power and a 2.3% better heat rate, and existing KB7S engines can be retrofitted. A single-shaft version serves constant-speed onshore and offshore oil and gas duty. Older nameplates include the steam-injected 501-KH, which a January 2000 Rolls-Royce Allison specification rates at 6,750 kW shaft power. Mobile versions are Siemens' Via5.8 and packager trailer units such as the Centrax CXA05 Mobile.

Configurations and options

Siemens Energy offers three combustion systems: standard combustion on gas or liquid fuel, Wet Low Emissions with steam or water injection, and Dry Low Emissions for gas fuel. Fuel options are natural gas, liquid fuel, dual fuel with automatic changeover at any load, and mid- to low-Btu gas. Packages include a synthetic lube oil system shared by engine and package, an on-skid fuel system, a choice of start systems, an acoustic enclosure, inlet filtration and a water wash system. The Via5.8 mobile unit adds on-trailer switchgear, a unit control panel, motor control center, auxiliary transformer and instrument air compressor, with a low-noise option rated below 85 dBA near field and 65 dBC far field. More than ten upgrades are offered, including DLE and dual-fuel conversions.

Compatibility and dependencies

Fuels include natural gas, liquid fuel (typically DF-2), mid- to low-Btu gas and, per the brochure, ethanol. Hydrogen blends are stated at up to 15% by volume with WLE burners on the product page and 30% with minimal hardware changes in the 2021 brochure. WLE needs a steam or water injection supply. Siemens rates at the generator terminals with no inlet or exhaust losses, so site output falls with heat and altitude. A fixed package occupies about 9 x 2.7 m plus the filter house and stack. The Via5.8 trailer needs no permanent foundation, has dual gas fuel inlets and a customer-supplied 480 V starting generator, and is rated for -40 to 50 C ambient per trade press.

Planning price band

Modelled planning estimate: $0.30M–$1.11M/MW · $298–$1,111/kW · $1.61M–$6M per unit (SGT-A05 KB7S, 5.4 MW; Used or refurbished, serviceable; very low confidence; gt-planning-v3, as of 2026-11-03). Private market information available. Not a quote or an observed sale price. Gas turbine generator-set package. Included auxiliaries, controls, emissions equipment (SCR), warranty and delivery terms vary by unit and are subject to confirmation. Not a project budget: BOP, installation and financing sit outside this band.

Small 4–6 MW aero. Private market information available.

What drives the price

Assessment: variant (KB5S versus KB7S or KB7HE), hours and starts since the last full overhaul, and whether a core engine exchange is due set the base value. Then come the combustion system (DLE, WLE or standard) and the fuels the unit is set up for, including biogas-only or liquid-only builds; package scope (bare core, skid package, or trailer unit with switchgear); generator voltage and frequency; trailer condition and road compliance for mobile units; and documented Siemens or authorized-center service history.

Lifecycle and maintenance

Siemens Energy states up to seven years of baseload operation between full overhauls on its product page and up to 32,000 hours in its 2021 brochure. The modular design allows module replacement on site and a direct core engine exchange in as little as 12 hours (product page) or a single 8-hour shift (brochure); the Via5.8 is designed for in-field servicing including gas turbine exchange. Service offerings are long-term programs, overhaul, field service, spare parts, service exchange, remote diagnostics, modernization and engine lease. Overhaul is also available from Siemens-authorized maintenance, repair and overhaul centers; Centrax received that status in 2018. Siemens Energy reports over 98% demonstrated availability and reliability and does not publish an MTBF figure for the SGT-A05 as of October 2026.

Thermal and emissions profile

Siemens Energy rates the DLE combustor at 25 ppmvd NOx or less at 15% O2 and 50 vppm CO on gas fuel without water injection, with emissions compliance down to 50% load; the brochure adds that DLE has achieved single-digit NOx depending on package and fuel. WLE uses steam or water injection for liquid fuel. Hydrogen is stated at up to 15% by volume with WLE burners on the product page and 30% on DLE and WLE in the 2021 brochure. Assessment: a 25 ppm guarantee meets the US KKKKa limits for small, low-utilization and temporary turbines but not the 15 ppm limit for medium turbines at high utilization.

Common failure points

• Hot-section blades, vanes and combustion liners — Coating loss, oxidation, cracking or burn-through as hours approach the full-overhaul interval
• DLE fuel system and combustor tuning — Emissions drift, combustion dynamics or failed emissions tests after fuel changes
• Reduction gearbox — Gear-tooth wear, bearing distress or rising vibration
• Generator — Winding insulation ageing or bearing wear
• Start system and controls — Obsolete control hardware or start-system faults that prevent a black start
• Trailer running gear and structure (mobile units) — Axle, brake, tire and landing-leg wear or frame damage from road moves
• WLE water or steam injection — Nozzle fouling or erosion from poor water quality

Identify the variant and its older name

• Siemens Energy's current SGT-A05 variants are the KB5S (4.0 MWe), KB7S (5.4 MWe) and KB7HE (5.8 MWe). Older units carry Allison or Rolls-Royce 501-K nameplates such as 501-KB5, 501-KB7 or the steam-injected 501-KH, and packaged sets carry packager names such as Centrax CX501. Match the engine nameplate, not the listing title, to the rating you are paying for.
• A KB7S can be upgraded to a KB7HE with Siemens' High Efficiency Compressor upgrade, which adds 8% power and improves heat rate by 2.3%. Ask whether the upgrade was done and by whom.

Mobile units: what a trailer-mounted SGT-A05 includes

• Siemens Energy's Via5.8 Mobile Power Unit carries the gas turbine, gearbox, generator, switchgear, unit control panel, motor control center, auxiliary transformer, lube oil cooler and fire protection on one five-axle trailer with two steerable front axles and ten landing legs. Siemens states on-site commissioning in under 2 hours in its 2021 brochure and full power in under four hours from arrival on its product page. The customer supplies a 480 V starting generator.
• Trade press gives the Via5.8 as 5.8 MWe at the generator terminals, 53 ft long, 8 ft 6 in wide, 13 ft 9 in high and 105,000 lb without a tractor, DOT compliant and rated for -40 to 50 C. The Centrax CXA05 Mobile is a comparable single-trailer package rated 5,624 kWe with a 4-hour setup at a new site.
• Turbomachinery Magazine describes the larger Via 7.9 (7.9 MWe, 63 ft long) as using a light-industrial gas turbine. Confirm the engine model in any Via offer.

US air rules for a trailer-mounted unit

• Under NSPS Subpart KKKKa a combustion turbine remains stationary even when it is mounted on a vehicle for portability; only portable turbines certified as nonroad engines under Clean Air Act title II are excluded. A unit kept at one source for 24 consecutive months or less can use the temporary subcategory: 25 ppm NOx on natural gas, with on-site proof of manufacturer certification to 25 ppm and a performance test within the prior five years.
• Relocating an existing turbine or changing its owner is not by itself a modification under 40 CFR 60.14(e)(6). Check the state permit requirements at each new site.

Rating basis and site output

• Siemens rates the SGT-A05 at ISO conditions with no inlet or exhaust losses, gaseous fuel and output measured at the generator terminals, assuming 98.5% generator efficiency and a 60 kW gearbox loss. Its brochure curves show output falling as ambient temperature rises, so ask for a site rating at the project's temperature, altitude and duct losses.

Overhaul position

• Siemens states up to seven years of baseload operation between full overhauls on its product page and up to 32,000 hours in its 2021 brochure. Price a unit near that interval as needing an overhaul or a core engine exchange, which Siemens puts at 8 to 12 hours on site.

Compare offers on

• Engine variant and nameplate — KB5S, KB7S or KB7HE, or the legacy 501-K designation, with engine, gearbox and generator serial numbers.
• Rating basis — ISO rating at the generator terminals versus site output at the project's ambient, altitude and duct losses.
• Overhaul position — Hours and starts since the last full overhaul against Siemens' stated interval, and whether a core engine exchange is included.
• Combustion and fuel — DLE, WLE or standard combustion; gas, liquid, dual-fuel or biogas set-up; NOx guarantee in ppm and mg/Nm3.
• Included scope — Bare core, skid package or trailer unit; generator, gearbox, switchgear, controls, filter house, stack and spares.
• Costs outside the offer — Transport and trailer permits, starting generator, fuel supply and compression, interconnection, air permits and commissioning.

Seller checklist

• Nameplate photographs for engine, gearbox and generator with variant and serial numbers
• Operating hours and starts since new and since the last full overhaul
• Overhaul and hot-section reports with dates and findings
• Borescope reports and images
• Combustion system, fuel set-up and the latest emissions test results
• Upgrade history (for example KB7S to KB7HE, DLE or dual-fuel conversion)
• Controls platform, software licences and drawings
• Generator insulation test results and gearbox inspection records
• For trailer units: trailer registration, axle and brake inspection records and a recent full-load test
• Included and excluded scope list with spares inventory

What sets the value

Value rests on records that place the unit in the SGT-A05 family: nameplate photographs and serial numbers for engine, gearbox and generator; the variant and upgrade history (for example KB7S to KB7HE or a DLE conversion); hours and starts since the last overhaul with the overhaul report; borescope images; emissions test results; controls software and drawings; and, for trailer units, the trailer registration, axle and brake inspections and a recent full-load test.

Can the SGT-A05 be used as a mobile power unit?

Yes. Siemens Energy sells the SGT-A05 Mobile Power Unit, the Via5.8: a single-trailer package rated up to 5.8 MWe, with on-site commissioning in under 2 hours per its 2021 brochure and full power in under four hours from arrival per its product page. Siemens' authorized packagers build similar trailer units, such as the Centrax CXA05 Mobile at 5,624 kWe.

How much power does an SGT-A05 produce?

At ISO conditions at the generator terminals, Siemens Energy rates the KB5S at 4.0 MWe (29.7%), the KB7S at 5.4 MWe (32.3%) and the KB7HE at 5.8 MWe (33.2%). Site output is lower in hot or high locations and after inlet and exhaust losses.

Is the SGT-A05 the same engine as the Rolls-Royce or Allison 501-K?

Yes. The SGT-A05 was formerly known as the 501-K. Siemens Energy describes it as aero-derived from the T56 turboprop, which Allison built; Rolls-Royce acquired Allison in 1995, and Siemens bought the Rolls-Royce Energy aeroderivative business in a deal that closed in December 2014.

Does a trailer-mounted SGT-A05 fall under US air rules for stationary turbines?

Yes. Under 40 CFR 60.4420a a turbine mounted on a vehicle for portability is still a stationary combustion turbine; only portable turbines certified as nonroad engines under Clean Air Act title II are excluded. A unit kept at one source for 24 months or less can fall in the KKKKa temporary subcategory, with a 25 ppm NOx limit on natural gas.

How often does an SGT-A05 need a full overhaul?

Siemens Energy states up to seven years of baseload operation between full overhauls on its product page and up to 32,000 hours in its 2021 brochure. A direct core engine exchange takes as little as 12 hours per the product page, or one 8-hour shift per the brochure.

Can the SGT-A05 burn hydrogen?

Siemens Energy states up to 15% hydrogen by volume with WLE burners on its product page and 30% on DLE and WLE systems with minimal hardware changes in its 2021 brochure. Confirm the emissions guarantee at the intended blend.

Inspection checklist

Read the engine nameplate and record the variant (KB5, KB5S, KB7, KB7S, KB7HE or KH) and the serial numbers of engine, gearbox and generator. Obtain hours and starts since new and since the last full overhaul, and compare them with Siemens' stated interval. Request borescope images and the last hot-section report. Confirm the combustion system (standard, WLE or DLE), the fuels the unit is set up for and the latest emissions test. Check the controls platform, start system and parts support with Siemens Energy or an authorized center. For a trailer unit, inspect axles, tires, brakes and landing legs, check the trailer's road registration, and witness a start to full load before payment.

Procurement channels

Siemens Energy supplies the engine through authorized packagers that build stationary and mobile generator sets, and sells its own Via5.8 mobile unit. Its 2021 brochure lists packagers in the UK (Centrax), North America (OnPower), China and Japan, plus authorized maintenance, repair and overhaul centers. Used engines and packages are advertised under the Centrax, Allison and Rolls-Royce names; listings seen in October 2026 ranged from contact for pricing to dated euro asking prices.

Regional notes

All three variants are offered for 50 Hz and 60 Hz. In the United States the KB5S, KB7S and KB7HE work out to about 51, 63 and 66 MMBtu/h HHV at ISO (calculated), which puts the KB5S at the 50 MMBtu/h small/medium boundary of NSPS Subpart KKKKa and the KB7 variants in the medium class. In the EU a rated thermal input of about 13.5-17.5 MW (calculated) places it under the Medium Combustion Plant Directive, whose 50 mg/Nm3 NOx limit for new gas-fired turbines is about what a 25 ppm guarantee equals (about 51 mg/Nm3). The engine is shock-qualified to Mil-S-901C.

Content owner: Gary Martin, SecondWatt