Gas Turbines in Power Generation: Aeroderivative or Heavy Duty Frame, and How to Decide

One decision determines almost everything about a gas turbine project, and in 2026 it is being made on availability rather than on efficiency.

Aeroderivative new-build lead times run roughly 12 to 24 months. Heavy duty frame lead times at major OEMs run 4 to 6 years.

That gap decides projects before efficiency, fuel flexibility or maintenance strategy enter the conversation. An operator who needs capacity in three years has one option regardless of which machine suits the duty better.

The rest of the decision is a set of trades with numbers attached. Aeroderivative run 34 to 42 percent simple-cycle efficiency, roughly 10 to 15 percent higher than a comparable frame. Frames reach 55 to 58 percent in combined cycle against 50 to 53 percent for aeroderivatives, and the latest heavy duty machines exceed 64 percent.

This guide covers what a gas turbine actually is, how the two platforms differ on every axis that matters, and what to specify.

What a Gas Turbine Is

A gas turbine is a continuous combustion engine that converts the chemical energy in fuel into mechanical shaft power, which a generator converts to electricity.

Continuous is the operative word. A reciprocating engine burns fuel in discrete, contained explosions in a cylinder. A gas turbine burns fuel continuously in a combustion chamber while air flows through it without stopping.

That distinction is the reason the two technologies behave so differently on vibration, maintenance, power density and emissions.

The three stages

A compressor draws in ambient air and raises its pressure. A combustion chamber mixes fuel with that compressed air and burns it continuously. The resulting high-temperature, high-pressure gas expands through turbine stages, spinning a shaft.

That shaft drives both the compressor and the generator. A substantial share of the turbine's gross work goes back into driving its own compressor, which is why compressor condition affects net output so directly.

The thermodynamic cycle is the Brayton cycle: compression, constant-pressure heat addition, expansion.

For component-level detail, see our gas turbine parts guide.

The Decision: Aeroderivative or Heavy Duty Frame

Industrial gas turbines come in two platforms, and the choice between them sets capacity, efficiency, start behavior, maintenance model and lead time simultaneously.

An aeroderivative gas turbine is derived from an aircraft engine core, adapted for stationary power. It is lightweight, compact, modular, and typically built on two or three shafts with a smaller rotor diameter.

A heavy duty frame gas turbine is purpose-designed for stationary service. It is heavier, larger, single-shaft in most configurations, uses hydrodynamic bearings, and is built for continuous operation at scale.

Turbomachinery Magazine's engineering comparison of the two platforms describes heavy frame units as slower in speed, narrower in operating speed range, heavier, larger, higher in air flow, slower to start, and requiring more time and spare parts for maintenance.

The traditional siting split

Aeroderivative have been preferred for remote and offshore applications, where weight, footprint and transportability matter. Heavy frames have been preferred for accessible base-load sites where size is not a constraint.

That split still holds, and lead time has started to override it.

Where reciprocating engines beat both

Below roughly 50 MW, a modern reciprocating engine achieves higher simple-cycle efficiency than either turbine platform, and it holds far more of its rating in hot conditions. For the full technology comparison, see our guide to power generation equipment compared.

Efficiency: Which Platform Wins Depends on the Cycle

Aeroderivative win on simple cycle efficiency. Heavy duty frames win on combined cycle efficiency. The reason is the same in both cases: pressure ratio.

Aeroderivative units typically run 34 to 42 percent simple-cycle efficiency, roughly 10 to 15 percent higher than a comparable heavy duty frame turbine.

In combined cycle the ranking reverses. Aeroderivative combined cycle thermal efficiency runs on the order of 50 to 53 percent, against 55 to 58 percent for a combined cycle using a heavy duty turbine. The latest heavy duty machines go further: Siemens Energy's SGT6-9000HL is rated at 655 MW in combined cycle at more than 64 percent efficiency.

Why the reversal happens

The aero derivative's higher pressure ratio extracts more work from the gas before it leaves the turbine, which is what makes the simple cycle efficient.

The consequence is a substantially lower exhaust temperature. A combined cycle recovers exhaust heat to raise steam, and a cooler exhaust produces less steam and less bottoming cycle output. On aeroderivative the lower exhaust temperature also makes it impractical to reheat the working fluid between bottoming cycle turbine stages.

The frame throws away more energy in the exhaust, and the steam cycle collects it.

State the basis

Efficiency figures are meaningless without a heating value basis. A figure quoted on lower heating value and the same machine quoted on higher heating value differ by roughly 10 percent on natural gas, which is larger than most differences being compared.

The OEM figures above are LHV. Require the basis in writing.

Site conditions change everything

Every efficiency and output figure is quoted at ISO reference conditions, and no plant operates there. For how ambient temperature, altitude and inlet losses derate a machine at your actual site, see our guide to gas turbine power stations and ISO rating.

Start Time: Define the Finish Line Before Comparing Minutes

Start time comparisons are routinely meaningless because the two platforms are measured against different finish lines.

Current OEM figures illustrate the problem. The GE Vernova LM6000 PF+ SPRINT is a 56.9 MW aeroderivative at 41.0 percent LHV efficiency, with 5-minute fast-start capability and a nominal ramp rate around 50 MW per minute. The GE Vernova 7HA.03 is a 430 MW heavy duty frame at 43.3 percent LHV, reaching full gas turbine load in 10 minutes at 75 MW per minute. Siemens Energy's SGT6-9000HL ramps at 85 MW per minute.

The arithmetic that resolves it

The frame adds more megawatts each minute. The aeroderivative traverses a much larger share of its rating over the same interval.

At 50 MW per minute on a 56.9 MW machine, the LM6000 covers roughly 88 percent of its rating in one minute. At 75 MW per minute on a 430 MW machine, the 7HA.03 covers roughly 17 percent.

If you need 50 MW in two minutes, the aeroderivative delivers it. If you need 300 MW in five minutes, the frame does.

Ask what the requirement actually is in megawatts and minutes, then compare machines against it, rather than comparing their headline start figures against each other.

Hot and cold starts

• A hot start follows a recent shutdown while the machine retains heat. A cold start follows an extended outage from ambient temperature.
• The difference is large on frame machines. Cold start times for leading large frame gas turbines run around 215 minutes, roughly 3.5 times their average hot start times.
• Aeroderivative, being lighter and having less thermal mass to manage, show far less variation. Hot and cold start classifications are frequently not needed for them at all.

Combined cycle changes the answer again

A combined cycle plant must bring the steam cycle up behind the gas turbine, which takes far longer than the gas turbine alone. A 10-minute gas turbine start does not produce a 10-minute plant start.

Pressure Ratio

Pressure ratio is the ratio of compressor discharge pressure to inlet pressure, and it is the single parameter that explains most of the difference between the two platforms.

Research into gas turbine performance puts the pressure ratios of most frame gas turbines in the range of around 12 to 24, while aeroderivative power generation turbines typically run relatively higher pressure ratios, up to 42.

The higher efficiencies of aeroderivative are mainly attributed to those higher pressure ratios.

What follows from it

Higher pressure ratio means more work extracted per unit of gas, which means higher simple cycle efficiency and lower exhaust temperature.

It also means tighter clearances, more compressor stages, and greater sensitivity to inlet conditions and fouling. For how fouling consumes performance and surge margin, see our guides to gas turbine casings and fouling and compressor stall and surge.

Maintenance: Different Models, Different Accounting

Frames and aeroderivative are maintained in fundamentally different ways, and the service contract accounting differs with them.

Frame machines have longer intervals between overhauls, often exceeding 30,000 operating hours, but the work is more comprehensive and time-intensive. The machine is opened on site.

Aeroderivative are maintained by module exchange. The gas generator core is removed and replaced with a spare, and the removed unit is overhauled in a shop. Turnaround is faster; the spare module and its lead time become the constraint.

The cycling accounting difference

This is the part that affects a service contract directly.

GE states that its aeroderivative solutions can perform frequent short cycles without changing maintenance intervals, while heavy duty service plans often count factored starts and hours.

Factored starts means each start is counted as a multiple of running hours against the maintenance interval, because a start consumes more component life than steady operation. A frame machine cycled daily reaches its overhaul interval far sooner than its running hours suggest.

On a cycling duty, confirm how the service agreement counts starts before comparing maintenance costs.

Lifecycle cost

Aeroderivative carry higher operating expenditure per kWh, driven by more frequent maintenance and greater sensitivity to fuel quality. Their fast start capability suits flexible and peaking operations where generation revenue is concentrated in a few hours.

Frames achieve lower lifecycle cost only at high, continuous utilization, where their combined cycle efficiency and longer intervals pay.

Staffing and insurance

Module exchange needs lifting capability and a logistics arrangement. On-site opening needs a larger maintenance organization and a longer outage window. Insurers assess maintenance regime and documented condition monitoring when pricing machinery breakdown risk.

For outage scheduling and the metrics that govern availability, see our gas turbine outage planning guide and our guide to power plant O&M metrics and contracts.

Lead Time: The Constraint That Decides Most Projects

New-build gas turbine lead times in 2026 run roughly 12 to 24 months for aeroderivative units against 4 to 6 years at major OEMs for heavy duty frames.

That is not a scheduling detail. It is the first filter in most selection decisions.

Why the gap exists

Heavy duty frame order books have been absorbed by data centre and utility demand, and manufacturing slots for the largest classes are committed years out. Aeroderivative production runs shorter cycles and draws on an aviation-derived supply chain.

What it means operationally

A project needing capacity within three years cannot specify a new heavy duty frame regardless of which platform suits the duty better.

That pushes projects toward aeroderivative, toward used and refurbished frame equipment, toward reciprocating engines, or toward mobile and rental solutions as a bridge.

The bridge-then-permanent pattern

Many operators now deploy fast-track capacity to meet an immediate need while a permanent plant proceeds on its own timeline. For how those timelines actually run from permitting to commercial operation, see our guide to fast-track power plant deployment. For what mobile units deliver, see our guide to mobile gas turbine power plants.

Financing

Lead time affects financing because it extends the period between capital commitment and revenue. A 4 to 6 year equipment lead time on a project with a 25-year life changes the return profile materially, and it should be modelled rather than treated as a schedule footnote.

Fuel Flexibility and Hydrogen

Gas turbines run on natural gas, liquid fuels including diesel and jet fuel, biogas and increasingly hydrogen blends, and heavy duty frames currently tolerate more variation than aeroderivative.

That is counterintuitive and it is the correct position. Heavy duty units generally tolerate lower-quality or non-standard fuels better than aeroderivative units, while aeroderivative require cleaner fuel and tighter fuel pressure control.

Hydrogen capability runs the same way

Heavy duty units currently offer broader hydrogen tolerance. GE's 6B platform is rated for blends running up to 90 percent hydrogen. Some aeroderivative platforms support hydrogen blending at lower percentages.

Hydrogen capability varies significantly by platform and configuration, and it should be confirmed against the specific turbine model and the site fuel supply rather than assumed from a manufacturer's general position.

The arithmetic nobody states

Hydrogen burns to water vapor, which is why it is described as clean at the point of combustion. The carbon reduction is smaller than the blend percentage suggests, because hydrogen has far lower volumetric energy density than methane. A blend stated as a percentage by volume delivers a considerably smaller percentage reduction in CO2.

For the full arithmetic, the OEM positions by platform and what the blend percentages actually deliver, see our analysis of hydrogen in gas turbines.

Dual fuel

Dual-fuel capability allows operation on liquid fuel when gas is unavailable. It adds a fuel system, storage and a changeover capability that must be tested rather than assumed. On sites where gas supply is the reliability risk, it is the difference between a plant and a decoration.

Configurations: Simple Cycle, Combined Cycle, Cogeneration

• Three configurations exist, and the choice sets both efficiency and start time.
• Simple cycle exhausts to atmosphere, runs 34 to 42 percent efficient on an aeroderivative, and starts in minutes. It suits peaking, reserve, bridging and mobile applications.
• Combined cycle adds a heat recovery steam generator and a steam turbine, recovering exhaust heat to produce additional electricity from the same fuel. It reaches 50 to 53 percent on aeroderivative and 55 to 58 percent on heavy duty frames, with the latest HL class above 64 percent, and it takes substantially longer to start.
• Cogeneration recovers exhaust heat as useful thermal energy rather than converting it back to electricity. Where a genuine year-round thermal load exists it reaches the highest total system efficiency of the three.

If you want combined cycle later

Specify it at the outset even if you build simple cycle first. The exhaust arrangement, the plot space, the water supply and the electrical layout all differ, and retrofitting an HRSG into a plant that did not plan for one is substantially more expensive than providing for it.

For configuration detail including balance of plant and duct firing, see our guide to gas turbine power stations.

Emissions and Control

Gas turbines produce significantly lower emissions of Sulphur dioxide, nitrogen oxides and particulate matter than coal-fired plant, and on natural gas they emit up to 50 percent less carbon dioxide.

NOx is the pollutant that drives control technology selection, and two approaches dominate.

Dry low NOx combustion, or DLN, reduces NOx formation by premixing fuel and air to lower flame temperature. It is the primary control on most modern machines and it requires periodic tuning to hold emissions across ambient and load ranges.

Selective catalytic reduction, or SCR, injects ammonia or urea across a catalyst in the exhaust, converting NOx to nitrogen and water. It adds capital cost, a small backpressure penalty and a continuing reagent cost.

The governing standard

40 CFR Part 60 Subpart KKKKa applies to stationary combustion turbines constructed, modified or reconstructed after 13 December 2024. It sets NOx limits by turbine category and, for units above 850 MMBtu/hr heat input operating above a 45 percent capacity factor, requires selective catalytic reduction.

A configuration that stays below a control technology threshold is sometimes worth choosing even at an efficiency penalty, because the avoided capital and operating cost of the control system can exceed the efficiency gain. That is a concept-stage decision.

Carbon capture

Carbon capture and storage can be applied to gas turbine plant, capturing CO2 from the exhaust for geological storage or industrial use. It carries a parasitic load and an efficiency penalty that must be modelled rather than assumed away, and it remains limited in commercial deployment on gas turbine power generation.

Outside the United States

The machines and the control technologies are the same. National emissions frameworks are not, and grid codes may impose frequency response and ramping requirements that influence platform choice as much as emissions limits do.

Applications

• Gas turbines serve seven application classes, and the binding requirement differs in each.
• Utility base load, where combined cycle efficiency dominates and heavy duty frames with a steam cycle are the standard answer.
• Peaking and reserve, where start time and ramp rate carry the revenue and aeroderivatives dominate.
• Grid stability and ancillary services, where fast ramping provides frequency regulation and voltage support as renewable penetration rises. A machine that reaches load in minutes can cover a cloud passing over a solar farm or a wind lull.
• Industrial captive power, where process steam demand frequently makes cogeneration the right configuration and the comparison is against a retail tariff rather than a wholesale price.
• Oil and gas, including mechanical drive for compression as well as power generation, frequently on remote sites with associated gas as fuel.
• Data centres, where time to power outranks efficiency, which favours simple cycle and mobile capacity over more efficient combined cycle.
• Remote, offshore and microgrid applications, where weight, footprint and transportability favour aeroderivatives, and where delivered fuel cost raises the value of efficiency.

Distributed and backup power

Gas turbines suit distributed energy and backup applications where rapid start-up, high reliability and fuel flexibility are critical. Integrating turbines with battery storage lets the storage cover the seconds before the turbine reaches load, which neither does alone.

For storage sizing and chemistry, see our guide to battery energy storage systems. For what condition monitoring and analytics genuinely deliver on an operating fleet, see our analysis of AI in plant operations.

What to Specify

• A turbine specification is reviewable only if it states the conditions, the basis and the test method.
• Output and heat rate at site conditions, not at ISO, with the correction curves annexed.
• The heating value basis, LHV or HHV, stated explicitly for every efficiency figure.
• The start requirement in megawatts and minutes, from the start condition you will actually experience.
• Ramp rate in MW per minute, and the proportion of rating that represents.
• Maintenance interval basis, including whether starts are factored and at what rate.
• Fuel specification including gas composition, pressure, and any hydrogen blend requirement now or anticipated.
• Emissions guarantee with the control technology named.

The test code

ASME PTC 22, Performance Test Code on Gas Turbines, governs output and heat rate testing. ISO 3977 defines the reference conditions at which ratings are quoted.

Name the test code and agree the correction curves before award. A performance guarantee stated at ISO reference conditions is effectively unenforceable, because the plant will never operate at 15°C and sea level with zero inlet losses.

What Prismecs Does

Prismecs delivers, installs, commissions, operates and maintains gas turbine power plant, and supplies equipment, with a delivered record in fast-track aeroderivative capacity.

Delivered project scope includes eight TM2500 dual-fuel units totaling 260 MW at Birr, Switzerland, built as a fast-track reserve plant online in six months on a compact site with a new 220 kV interconnection and engineered noise controls; four TM2500 units totalling 110 MW at Duqm, Oman, kept grid-ready with resident O&M crews, CMMS and parts support; an LM2500XPRESS plant at Miaoli, Taiwan delivered in ten months; three LM6000PC units adding 150 MW of fast-start reserve; and an LM6000 fleet decommissioned in Norway, transported and recommissioned at a new site.

The TM2500, LM2500 and LM6000 are aeroderivative machines, which is the platform this article identifies as the available option on constrained timelines. Birr at six months and Miaoli at ten are the relevant references for anyone whose binding constraint is time rather than efficiency.

Capability spans power generation asset services for the equipment, EPCM services for project delivery, I&C services for installation, commissioning and controls, O&M services for the operating phase, ready-to-ship equipment inventory, distributed energy solutions for microgrid and storage integration, and technology and consulting for options analysis. Equipment sourcing and market comparison run through eINDUSTRIFY.

Prismecs is OEM-agnostic, which on a platform selection matters because the party comparing aeroderivative against frame is not selling one of them.

Apply this article's criteria to any proposal, including ours. Ask for output and heat rate at your site conditions with the basis stated. Ask what the start requirement is in megawatts and minutes rather than accepting a headline figure. Ask whether starts are factored in the maintenance agreement. Ask for the current lead time in writing.

To discuss turbine selection, capacity addition or an operations and maintenance scope, send your required capacity, site location and elevation, design ambient temperature, duty profile, fuel position and target in-service date to sales@prismecs.com or call +1 (888) 774-7632.

Frequently Asked Questions

Is a gas turbine an internal combustion engine?

It is a continuous combustion engine, which is a distinct category. A reciprocating internal combustion engine burns fuel in discrete, contained events inside a cylinder. A gas turbine burns fuel continuously in a combustion chamber while air flows through it without interruption. That difference in combustion mode is why the two technologies behave so differently on vibration, power density, emissions and maintenance.

What is the difference between an aeroderivative and a heavy duty frame turbine?

An aeroderivative is adapted from an aircraft engine core: lightweight, compact, usually two or three shafts, higher pressure ratio, maintained by module exchange. A heavy duty frame is purpose-built for stationary service: heavier, larger, usually single-shaft, lower pressure ratio, higher air flow, maintained by opening the machine on site. The platform choice sets capacity, efficiency, start behaviour, maintenance model and lead time together.

Which type of gas turbine is more efficient?

It depends on the cycle. Aeroderivatives run 34 to 42 percent simple-cycle efficiency, roughly 10 to 15 percent higher than a comparable heavy duty frame. In combined cycle the ranking reverses: aeroderivatives reach 50 to 53 percent against 55 to 58 percent for heavy duty, with the latest HL-class machines above 64 percent. The reversal happens because higher aeroderivative pressure ratios produce a cooler exhaust.

Why does aeroderivative combined cycle underperform heavy duty?

Because of exhaust temperature. The aeroderivative's higher pressure ratio extracts more work from the gas before it leaves the turbine, which makes the simple cycle efficient and leaves the exhaust cooler. A combined cycle recovers exhaust heat to raise steam, so a cooler exhaust produces less bottoming cycle output. The lower temperature also makes reheat between bottoming cycle turbine stages impractical.

Which gas turbine starts faster?

Measured as a share of rating, the aeroderivative. The GE Vernova LM6000 PF+ SPRINT is 56.9 MW with 5-minute fast start and a nominal ramp around 50 MW per minute, covering roughly 88 percent of its rating in a minute. The GE Vernova 7HA.03 is 430 MW reaching full load in 10 minutes at 75 MW per minute, covering roughly 17 percent. Define the requirement in megawatts and minutes first.

What is the difference between a hot start and a cold start?

A hot start follows a recent shutdown while the machine retains heat. A cold start begins from ambient after an extended outage. The gap is large on frame machines: cold start times for leading large frame gas turbines run around 215 minutes, roughly 3.5 times their average hot start times. Aeroderivatives have less thermal mass to manage and show far less variation, often needing no such classification.

What pressure ratios do gas turbines run at?

Most frame gas turbines run pressure ratios of around 12 to 24. Aeroderivative power generation turbines typically run higher, up to roughly 42. The higher efficiencies of aeroderivatives are mainly attributed to those higher pressure ratios. The trade-off is tighter clearances, more compressor stages, and greater sensitivity to inlet air condition and fouling than a frame machine experiences.

How long are gas turbine lead times in 2026?

Roughly 12 to 24 months for aeroderivative new-build, against 4 to 6 years at major OEMs for heavy duty frames. That gap is the first filter in most selection decisions, because a project needing capacity within three years cannot specify a new heavy duty frame regardless of technical fit. The alternatives are aeroderivatives, used or refurbished equipment, reciprocating engines, or mobile capacity as a bridge.

Which gas turbine handles hydrogen better?

Heavy duty frames, currently. They generally tolerate lower-quality and non-standard fuels better than aeroderivatives, including high-hydrogen blends, with GE's 6B platform rated for blends up to 90 percent hydrogen. Some aeroderivative platforms support hydrogen blending at lower percentages. Capability varies significantly by platform and configuration and should be confirmed against the specific model and the site fuel supply.

Does a 30 percent hydrogen blend cut CO2 by 30 percent?

No. Hydrogen burns to water vapour and produces no CO2 at the point of combustion, but it has far lower volumetric energy density than methane. A blend stated as a percentage by volume therefore displaces a considerably smaller percentage of the energy, and delivers a correspondingly smaller CO2 reduction. The blend percentage and the emissions reduction are different numbers and should never be used interchangeably.

How do maintenance models differ between the two platforms?

Frames have longer intervals, often exceeding 30,000 operating hours, with more comprehensive and time-intensive work performed by opening the machine on site. Aeroderivatives are maintained by module exchange, where the gas generator core is swapped and the removed unit overhauled in a shop. Turnaround is faster on the aeroderivative, and the spare module and its lead time become the constraint.

What are factored starts and why do they matter?

A method of counting each start as a multiple of running hours against the maintenance interval, because a start consumes more component life than steady operation. Heavy duty service plans often count factored starts and hours. GE states its aeroderivative solutions can perform frequent short cycles without changing maintenance intervals. On a cycling duty, confirm how the service agreement counts starts before comparing maintenance costs.

Which platform has lower lifecycle cost?

Aeroderivatives carry higher operating expenditure per kWh, driven by more frequent maintenance and greater fuel quality sensitivity, but their fast start suits flexible and peaking duty where revenue concentrates in few hours. Heavy duty frames achieve lower lifecycle cost only at high continuous utilisation, where combined cycle efficiency and longer overhaul intervals pay back their larger capital and slower response.

What emissions standard applies to new gas turbines in the US?

40 CFR Part 60 Subpart KKKKa applies to stationary combustion turbines constructed, modified or reconstructed after 13 December 2024, setting NOx limits by turbine category and requiring selective catalytic reduction for units above 850 MMBtu/hr heat input operating above a 45 percent capacity factor. Dry low NOx combustion is the primary control on most modern machines, requiring periodic tuning across ambient and load ranges.

Tags: Gas Turbines Aeroderivative Turbines Heavy Duty Frame Turbine Efficiency Power Generation