Combined Cycle Power Plants: How to Build in Phases From Simple Cycle to 2×1
Combined cycle power plants turn more of every unit of gas into electricity than simple cycle plants do. For owners facing rising fuel costs and long equipment queues, that efficiency matters. The challenge is timing. Full combined cycle power plants take longer to build, and many projects need power sooner.
A phased build solves much of that problem. You install gas turbines in simple cycle first, start earning, and add the steam side later. This guide explains how combined cycle power plants work, what it costs, how phasing changes risk and schedule, and how to choose a contractor. It uses the FX-45 2×1 block from USP&E as an example. Every FX-45 figure comes from the published FX-45 product page.
USP&E has supplied 25k MW of power and built 150+ power stations across 45+ countries since 2002. USP&E holds ISO 9001:2015 and ISO 45001:2018 certification. USP&E delivers EPC (Engineering, Procurement and Construction) and O&M (Operations and Maintenance), so the guidance reflects how plants are built and run.
For the equipment side, read the companion guides on what a gas turbine generator package includes and behind the meter onsite power.
What Are Combined Cycle Power Plants? Configuration and Ratings
They are plants that use gas turbine exhaust heat to make steam, which drives a steam turbine for extra power. A combined cycle gas turbine plant has three main parts: gas turbines, a heat recovery steam generator (HRSG) behind each one, and a steam turbine. The steam side is called the bottoming cycle.
The U.S. Energy Information Administration reports that the most common arrangement is two gas turbines feeding one steam turbine, known as the 2×1 configuration. See its Today in Energy article, Most combined-cycle power plants employ two combustion turbines with one steam turbine (2022).
Many combined cycle power plants follow that pattern, and so does the FX-45 block. Two FX-45 packages each feed an HRSG, and one steam turbine generator sits between them.
FX-45 2×1 block ratings
|
Parameter |
FX-45 published value |
|
Configuration |
2×1: two gas turbines, two HRSGs, one steam turbine |
|
Gas turbine output |
90 MW (two 45 MW packages) |
|
Block output |
About 135 MW, indicative |
|
Exhaust flow |
167 kg/s per turbine |
|
Exhaust temperature |
550 degrees Celsius |
|
Condenser |
Air-cooled where water is scarce, wet where the site permits |
|
Controls |
One integrated control system across gas and steam islands |
Source: USP&E FX-45 page. Ratings are at ISO conditions: 15 degrees Celsius, sea level, 60% relative humidity, natural gas, at the generator terminals and a power factor of 0.8.
How a combined cycle gas turbine plant runs also matters. Gas turbines can start and change load quickly, while the steam side responds more slowly because the HRSG and steam turbine must warm up. Many plants therefore run at steady output for long periods, which is where the fuel saving pays back best. A combined cycle gas turbine plant suits base load and long daily runs more than short peaking duty. Owners who expect frequent starts should discuss cycling limits and maintenance effects with the contractor before choosing the configuration.
The block scope also covers feedwater, deaerator, condensate, blowdown and demineralised water systems. SCR, remote monitoring, O&M and an LTSA (Long-Term Service Agreement) are optional.
Combined Cycle Power Plants Cost and Total Installed Cost: What Owners Should Budget
Combined cycle power plants cost more to build than simple cycle plants but use much less fuel per unit of power. The figures below are indicative third-party references for new U.S. plants, not USP&E prices. FX-45 pricing is issued under a non-disclosure agreement.
Combined cycle compared with simple cycle
|
Combined cycle power plants and alternatives |
Total overnight cost |
Fixed O&M |
Variable O&M |
Heat rate |
|
Combined cycle, multi-shaft |
About $1,032/kW |
About $12.69/kW per year |
About $3.57/MWh |
6,226 Btu/kWh |
|
Combined cycle, single shaft |
About $1,086/kW |
About $16.23/kW per year |
About $3.49/MWh |
6,226 Btu/kWh |
|
Industrial frame simple cycle |
About $1,158/kW |
About $7.18/kW per year |
About $4.17/MWh |
9,142 Btu/kWh |
|
Aeroderivative simple cycle |
About $2,275/kW |
About $9.99/kW per year |
About $5.97/MWh |
9,447 Btu/kWh |
Source: U.S. Energy Information Administration, Assumptions to the Annual Energy Outlook 2026, Table 3 (April 2026, 2025 US dollars). The EIA reference plants are much larger than a 135 MW block, so costs per kW for smaller plants may differ.
Heat rate shows the fuel benefit. Based on these EIA figures, combined cycle power plants need about 32% less fuel per kWh than an industrial frame simple cycle plant. That share was calculated by USP&E from the EIA heat rates. The FX-45 page states a similar effect: roughly 50% more output from the same fuel.
The equipment is only part of the bill. In the Sargent & Lundy reference study for the EIA, Capital Cost and Performance Characteristics for Utility-Scale Electric Power Generating Technologies (January 2024), costs are split across equipment, labour, materials, engineering, fees, contingency and owner’s costs. A full budget for a 2×1 block should cover the steam island, water treatment, condenser, civil works, transformer and grid connection.
Phased vs Full Build Combined Cycle Power Plants: Schedule, Risk, and Warranty
A phased build gets power and revenue flowing earlier. The FX-45 page describes the approach: energise in simple cycle first, then add the bottoming cycle during a planned outage. The gas turbine package does not change, so the site keeps one equipment standard.
Phased build compared with full build
|
Factor |
Phased build |
Full build |
|
First power |
Earlier, from gas turbines in simple cycle |
Later, when the whole plant is complete |
|
Early efficiency |
Simple cycle heat rate until the steam side is added |
Combined cycle heat rate from the start |
|
Capital timing |
Spread across two stages |
Concentrated up front |
|
Construction risk |
Steam island work beside an operating plant |
One construction programme |
|
Layout |
Must reserve space for HRSGs and steam turbine |
Built as one design |
|
Outage need |
Planned outage to tie in the bottoming cycle |
None for conversion |
Phasing combined cycle power plants only works if it is designed in from day one. The site layout must leave room for each heat recovery steam generator and the steam turbine. Exhaust ducts, foundations and controls should be planned for the final 2×1 configuration. The FX-45 page states the package is combined cycle ready as built.
Equipment lead times make phasing more attractive. The Electric Power Research Institute (EPRI) reported in Utility Dive in March 2026 that large new gas turbines take more than five years from order to delivery. USP&E states the FX-45 is delivered in 18 to 24 months from slot reservation, with first deliveries from 2028. USP&E explains overall schedules in its guide to how long it takes to build a power plant.
Fuel Type Comparison
Figures are indicative third-party references for new U.S. plants, not USP&E prices.
|
Fuel Type |
CapEx Range |
OpEx Range |
Typical Lead Time |
Best Application |
|
Natural gas, combined cycle |
About $1,032 to $1,086/kW (EIA 2026) |
About $12.69 to $16.23/kW per year plus about $3.5/MWh (EIA 2026) |
About 40 to 42 months from development start, including 22 to 24 months construction (Sargent & Lundy for EIA, 2024) |
Base load where fuel efficiency matters most |
|
Natural gas, industrial frame simple cycle |
About $1,158/kW (EIA 2026) |
About $7.18/kW per year plus $4.17/MWh (EIA 2026) |
More than five years for large new units (EPRI 2026); FX-45 18 to 24 months from slot reservation |
First phase of a phased build |
|
Natural gas, aeroderivative simple cycle |
About $2,275/kW (EIA 2026) |
About $9.99/kW per year plus $5.97/MWh (EIA 2026) |
18 to 36 months for smaller new units (EPRI 2026) |
Peaking and fast start |
|
Diesel, containerised gensets |
About $650 to $880/kW installed (NREL REopt defaults) |
About $10 to $20/kW per year fixed, plus fuel (NREL REopt defaults) |
Often under 90 to 120 days, site dependent |
Standby and bridge supply |
|
HFO (Heavy Fuel Oil), engine power station |
About $800 to $1,000/kW, medium speed engines (IDB Invest, 2010 US dollars) |
Typically 9 to 14 months from deposit |
Remote base load without gas |
Sources: EIA, Assumptions to the Annual Energy Outlook 2026, Table 3; EPRI in Utility Dive (2026); USP&E FX-45 page. CapEx means capital expenditure and OpEx means operating expenditure. Diesel: NREL REopt model default values (REopt generator defaults, checked 2026). HFO: IDB Invest, Liquid and Gaseous Fossil Fuel Power Plant Guidelines, citing 2010 cost data, so treat it as an older reference.
Gas supply drives long-term cost. The International Energy Agency tracks natural gas markets and supply, which helps owners test fuel price assumptions. Where a site also needs heat, combined heat and power may suit better. The U.S. Department of Energy explains the differences in its combined heat and power basics, and USP&E covers delivery in its combined heat and power EPC guide.
Five Steps to a Phased Build of Combined Cycle Power Plants
Phased combined cycle power plants follow five broad steps. Each one builds on the last, and the early decisions matter most.
Step 1: Design for the final plant
Lay out the site for the full 2×1 block from day one. Reserve space for both HRSGs, the steam turbine, the condenser and water treatment. Plan exhaust ducts, foundations, cable routes and control system capacity for the final configuration.
Decide the cooling method at this stage too. An air-cooled condenser needs more space, while wet cooling needs a reliable water source and a discharge permit. Changing that choice later can force a new layout, so settle it while the site is still empty. Early agreement on access roads and crane positions also pays off when the heavy steam island equipment arrives.
Step 2: Install and energise the gas turbines
Install the gas turbine packages and run them in simple cycle. The plant starts producing power and revenue while the steam side is still being designed or financed. On the FX-45 approach, two 45 MW packages provide 90 MW in this phase.
Step 3: Build the steam island alongside
Build the HRSGs, steam turbine, condenser and water systems next to the operating plant. Careful site management keeps construction traffic and lifting away from live equipment.
Step 4: Tie in during a planned outage
Connect the gas turbine exhaust to the HRSGs during a planned outage. Agree the outage window with the grid operator or offtaker early, so lost revenue is kept to a minimum.
Step 5: Commission and optimise in combined cycle
Commission the steam turbine and integrated controls, then run performance tests. The block then operates in combined cycle at about 135 MW indicative output, on the FX-45 example.
What each step protects in combined cycle power plants
|
Step |
Main risk it controls |
|
Design for the final plant |
Rework and lost space when the steam side is added |
|
Energise the gas turbines |
Delayed revenue |
|
Build the steam island alongside |
Safety and disruption to the operating plant |
|
Tie in during a planned outage |
Unplanned downtime and lost sales |
|
Commission and optimise |
Output and heat rate below expectations |
Owners of combined cycle power plants who follow these steps in order usually find the conversion predictable. Owners who skip the first step often pay for it in the fourth.
Case Studies: Combined Cycle Power Plants in Real Projects
No FX-45 combined cycle block has been delivered yet, because first deliveries are stated from 2028. USP&E only publishes approved case studies.
A typical phased project for combined cycle power plants starts with simple cycle units to deliver early power, with space, permits and tie-in points reserved for the heat recovery steam generator and steam turbine. The bottoming cycle is then added once load and finance allow. USP&E supports engineering and delivery with a full complement of mechanical, electrical, process control and implementation engineers and staff across 45+ countries.
General lessons from phased projects, not from a specific project:
- Owners who reserve space and tie-in points from day one avoid costly rework later.
- Owners who plan the conversion outage with the grid operator protect revenue.
- Owners who standardise gas turbines across phases simplify spares and training.
How to Choose a Contractor for Combined Cycle Power Plants: 10 Criteria
- Combined cycle experience. Ask for references covering both gas and steam islands. Steam cycle integration is a separate skill.
- Phasing design. The contractor should design the simple cycle phase for the final layout. Ask to see the tie-in plan.
- Water strategy. Confirm whether the plant uses air-cooled or wet cooling. Water availability often decides this.
- Integrated controls. One control system across gas and steam islands simplifies operation. Ask how it is delivered.
- Performance guarantees. Ask for guaranteed output and heat rate at site conditions. Check how they are tested.
- Schedule realism. Compare the stated schedule with equipment lead times. Ask what drives the critical path.
- Emissions plan. Confirm NOx levels and whether SCR is needed. Match them to your permit.
- Engineering depth. In-house engineering reduces interface risk. USP&E provides power plant engineering across gas and steam systems.
- O&M capability. Combined cycle power plants need skilled operators. USP&E offers power plant operations and maintenance.
- Certification and compliance. Look for ISO 9001 and ISO 45001 certification and a written compliance policy. USP&E holds ISO 9001:2015 and ISO 45001:2018 certification.
FAQ: Combined Cycle Power Plants
How does a combined cycle plant work?
Gas turbines generate power and send hot exhaust to a heat recovery steam generator. The steam drives a steam turbine for extra power from the same fuel.
What does 2×1 mean?
It means two gas turbines feed one steam turbine. The EIA reports this is the most common arrangement for combined cycle power plants.
How much more efficient is combined cycle?
Based on EIA 2026 heat rates, combined cycle power plants need about 32% less fuel per kWh than an industrial frame simple cycle plant. The FX-45 page states roughly 50% more output from the same fuel.
Can a simple cycle plant be converted later?
Yes, if it is designed for it. The FX-45 approach is to energise in simple cycle first and add the bottoming cycle in a planned outage.
How big is an FX-45 combined cycle block?
Two 45 MW packages give 90 MW of gas turbine output. With the steam turbine, the block output is about 135 MW, indicative.
What does combined cycle cost?
As indicative references, the EIA put new combined cycle power plants at about $1,032 to $1,086 per kW in 2025 dollars. FX-45 pricing is issued under a non-disclosure agreement.
Does combined cycle need a lot of water?
It can, but air-cooled condensers reduce water use. The FX-45 block uses an air-cooled condenser where water is scarce and wet cooling where the site permits.
Key Takeaways: Combined Cycle Power Plants
- Combined cycle power plants turn more of each unit of gas into power than simple cycle.
- The 2×1 configuration is the most common arrangement for combined cycle power plants.
- A phased build brings first power earlier and spreads capital.
- Phasing must be designed in from day one: layout, ducts, foundations and controls.
- Use cited third-party costs to test budgets, and get a site-specific quotation.
Well-planned combined cycle power plants can start earning in simple cycle and grow into full efficiency. Send USP&E your site location, gas analysis, frequency, voltage and power date, and its engineers will help you plan each phase.
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