It has long been accepted wisdom in power generation that bigger equals more efficient. The bigger is better concept is attractive because it was true—until recently.

The core belief that larger turbines and thermal power plants are more efficient is reinforced by the countless instances in daily life where scale delivers efficiency. Trains and buses use much less fuel per person than cars; apartment buildings require far less energy per resident than single-family homes; and Costco’s massive purchasing volume drives down costs for customers. 

Like so much in the power sector these days, the conventional wisdom that size equals greater efficiency is being challenged—not by ideology, but by significant advancements in generator technology. Turbine efficiency illustrates this new dynamic. Smaller turbines 25 MW and below deliver efficiency in the low 30% range while larger turbines 50 MW or larger push efficiency to the high 30% range. By contrast, advanced generation technology can achieve efficiency above 40% at sub-MW scale. 

The power sector spent a century training itself to think that bigger is more efficient, more economical, and more practical. Now that more affordable small-scale generation can match large-scale efficiency, those old assumptions deserve a second look.

When critical facilities demand near-perfect, 99.9% uptime or better, the conventional approach of installing multiple large-scale power resources inevitably results in massive and expensive overbuild. But what if maintaining high efficiency at a much smaller, modular scale could deliver improved reliability at a fraction of the cost? The answer to that question emerges when you ask the right questions about how reliability is achieved and what it actually costs.

How much additional capacity does 99.9% reliability actually require?

Nobody would argue that reliability is optional, especially at critical facilities—like data centers, manufacturing plants, and semiconductor fabs—when downtime costs millions. The question is how much redundant capacity is enough?

The traditional answer: a lot. The math doesn’t lie. Let’s say you want to serve a 100 MW load at 99.9% availability using 50 MW generators. And assume each of the individual generators has a 5% outage rate. To deliver 99.9% reliability, it will require four 50 MW generators—a total of 200 MW.

Now consider how much capacity you’ll need if you use 3 MW generators with the same 5% outage rate. The math is straightforward, but the answer may be surprising: 99.9% reliability for the same 100-MW load requires approximately 114 MWs, almost half the 200 MW needed with the larger units. The relationship isn't linear—it's exponential. The larger each generator is relative to total load, the more total capacity you need to maintain reliability when one fails. 

When individual units represent a fraction of total capacity, their failure barely registers at the system level.

Why haven’t small generators been the standard approach?

The answer to this question is simple: until recently, it wasn't possible. The efficiency gains that drove a century of power sector development came primarily from scale. The bigger is better paradigm wasn't just conventional wisdom—it was a practical engineering reality.

No longer. Today, small-scale generation can rival large-scale thermal efficiency while offering flexibility in capacity deployment.

How does this change the total cost equation?

The technology advances that enable small generators to deliver high efficiency fundamentally change the economics—but only if you look at costs holistically. Indeed, procurement teams typically focus on dollars per MW as the primary capital cost metric. 

But that perspective obscures the financial reality that really matters: the total capital needed for availability adjusted capacity. 

When a site requires significant overbuild to meet high reliability targets, a simple $/MW metric at a unit level no longer captures the true cost of power. Instead, the relevant metric is the total capital per MW of reliable capacity delivered, which more accurately reflects how much installed capacity is needed to confidently serve the load.   

What happens when modular units need maintenance?

Beyond capital costs, modularity delivers operational advantages that large generators simply cannot match. The overbuild penalty with large generators exists precisely because of the realities of maintenance. Large, 50-MW turbines require maintenance that takes them offline for hours and even days. When a single unit goes down, it represents a significant percentage of total capacity–which is exactly why the system requires so much redundancy to maintain reliability during planned and unplanned outages. 

When routine maintenance is required on individual modular generators, the impact on system performance is minimized. Individual units can rotate through service schedules without affecting total site availability. With 50 MW of modular generators, there is a high likelihood that close to 50 MW will always be operational. The same redundancy that protects against unexpected failures also makes planned maintenance transparent. Redundancy isn't something you build for emergencies and hope never to use—it's how the system functions normally.

Where does modularity make the most difference?

The modularity advantage is most pronounced below about 300 MW—where the overbuild penalty for large generators becomes severe. But even at much larger scales, the same principle holds. 

The technology is ready. What’s needed is a mindset shift away from forcing load requirements to conform to available generator sizes to one that more precisely matches generator size to load requirements.