The 50% load factor: why South Africa’s gas commitment is a bridge, not a highway

South Africa’s Integrated Resource Plan (IRP) 2025 has drawn sharp criticism for committing to 16,000 MW of new gas-to-power capacity by 2039. Opponents argue that a minimum 50% load factor binds the country to a long-term carbon lock-in, stalling the transition to clean energy. 

This view misinterprets both the engineering function of mid-merit power and the legal mechanisms that govern modern energy assets. From Wärtsilä’s perspective as a global flexibility partner, gas at a 50% load factor is a bridge engineered to balance renewables, not a highway built to compete with them. And the difference is written directly into the contract and the technology itself. 

Balancing duty vs. baseload 

In order to effectively meet the demands of varying load factors driven by intermittent renewable energy (RE), a balanced approach is required. It is a common misconception that a 50% load factor indicates baseload operation; in reality, it represents mid-merit balancing duty.  

The role of these proposed plants is not to run continuously, but to provide firm, flexible capacity that maintains grid stability.  

It is important to clarify that a 50% load factor does not necessarily mean the plant is operating at 100% load for 50% of the time. Rather, the load and operating hours vary significantly across each day, week, month, and year. 

The Wärtsilä advantage  

As South Africa’s energy transition accelerates, the increasing penetration of renewables will inevitably drive average load factors below 50%. This is where Wärtsilä differentiates itself from traditional turbines: 

• Cost-effective flexibility: We provide the ability to balance intermittency cost-effectively, even as load factors decline. 
• Repeatable high frequency: Our assets are designed for the high-frequency starts, stops, and ramping required to stabilize a grid dominated by variable renewables.

This is not a theoretical model, but a proven operational strategy. The UK successfully decarbonised its grid largely by utilising gas assets flexibly to manage variability while its renewable capacity scaled, demonstrating that the ability to perform in a low-load-factor environment is the critical requirement for a modern, reliable power system. 

Lock-in is a contract problem 

The risk of asset lock-in is valid, but it is fundamentally a regulatory and contractual issue rather than an inherent flaw of thermal power. Capital can be bound to strict parameters from the outset. 

A short, controlled bridge is maintained through explicit contractual mechanisms: 

• Conversion deadlines that mandate a transition to alternative fuels. 
• Emissions intensity floors that lower permissible carbon output over time. 
• Taper clauses on capacity payments that reduce financial incentives as the renewable grid matures. 
• Decommissioning triggers that tie the asset’s lifespan to specific grid milestones. 
  

These mechanisms convert what critics see as a blank cheque into a capped facility with a defined expiration date. 

Engineering the fuel switch with Wärtsilä technology 

From a technology perspective, future-proofing can be embedded into the hardware on day one. Wärtsilä’s modular reciprocating engine plants are designed to adapt to the energy landscape from the start. Whether the initial operation begins with natural gas or liquid fuels, these assets are engineered to be converted to sustainable fuels or green hydrogen as supply chains mature and availability increases. 

Since the generation asset is built to survive a fuel switch, the physical infrastructure remains viable in a net-zero framework without creating stranded capital. 

The realistic framework 

An energy transition requires grid stability before it can absorb intermittent renewables at scale. Managing a 50% load factor under strict, tapering regulatory frameworks and deploying flexible, modular technology provides the necessary foundation to deploy wind and solar safely. 

When the contract limits the timeline and the technology allows for total fuel flexibility, the investment ceases to be a long-term threat to decarbonisation. It becomes the mechanism that enables it.