Wind turbine net capacity factor: is 50% the new normal?

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Anyone who hangs around in the comments section of sites covering wind energy knows one thing — clean energy haters love to talk about wind turbine capacity factor. In particular, they love to chant the now quite untrue claim that wind turbines have a capacity factor of 20-30%.If you’re not familiar with capacity factor, it is how much electricity a power plant actually produces compared to how much it would produce if it operated at full nameplate capacity 100% of the time.No power plant operates at 100 per cent capacity factor. NREL’s new Transparent Cost Database shows the following capacity factors:

– Natural gas combustion turbines — Minimum: 10%; Median: 80%; Maximum: 93%
– Natural gas combined cycle — Minimum: 40%; Median: 84.6%; Maximum: 93%
– Coal, pulverized & scrubbed — Minimum: 80%; Median: 84.6%; Maximum: 93%
– Nuclear — Minimum: 85%; Median: 90%; Maximum: 90.24%
– Biopower — Minimum: 75%; Median: 84%; Maximum: 85%
– Hydropower — Minimum: 35%; Median: 50%; Maximum: 93.2%
– Enhanced geothermal — Minimum: 80%; Median: 90%; Maximum: 95%
– Solar PV – Minimum: 16%; Median: 21%; Maximum: 28%
– Offshore wind – Minimum: 27%; Median: 43%; Maximum: 54%
– Onshore wind – Minimum: 24%; Median: 40.35%; Maximum: 50.6%

Where Does Capacity Factor Fit Into Things?

Now, before moving on to the focus of this article, here’s one more thing to note:

Clean energy haters love to talk about capacity factor because it’s clearly a metric wind, solar, and hydro don’t win at (though, geothermal and biopower actually do very well). However, capacity factor by itself is really not that important. What’s important is the total cost of producing electricity. In the energy field, levelized cost of energy (LCOE) is one of the most important metrics. This is “an estimate of total electricity cost including payback of initial investment and operating costs,” as NREL writes.

Capacity factor plays a role in LCOE, of course, but so does free fuel (i.e. wind and sunshine). (In a perfect market, LCOE should also include the cost of pollution, which is not the case at all in the US today.)

Even without the cost of pollution figured in, if you look at NREL’s LCOE tab, onshore wind energy has a median of $0.05/kWh. The only energy source that beats that is hydropower ($0.03).

So, the point is, onshore wind energy is already essentially the cheapest option for new electricity (new hydro is not so cheap — that low figure is based on very old dams), even with NREL’s median capacity factor of 40.35%.


Technology Changes

Wind power is still a relatively new electricity option. The technology is still improving, becoming more and more efficient. And, as a part of that, there has been what is essentially a breakthrough in net capacity factor of various turbines in just the last two years.

Chris Varrone of Riverview Consulting, a friend of ours and true expert in this arena, recently noted in an email to me that this is due to a “proliferation of ’stretch rotor’ machines like the GE 100-1.6MW and the V100-1.8MW and V112-3.0MW…. such machines can often hit 50% capacity factor onshore.”

In other words, new wind turbines are regularly hitting 50% capacity factor, much better than that antiquated 20-30% clean energy haters love to throw around!

More from Chris: “this contrasts with low 30s for the last generation of rotors (e.g., V80-2.0MW) — it is changing the game.”

NREL’s minimum of 24% is old news, old technology. Even turbines in the 30s are old technology now. And the median is being brought down by these older turbines.

New wind turbines are more efficient. And, thus, new wind power is even cheaper. It is now at an all-time low, in fact.

One more note from Chris: “LCOE has declined by 33-45% in the past 3 years in the US!”

Next Time You’re in a Conversation with a Wind Energy Hater

What are the takeaway points?

  1. Wind turbine capacity factors are often 50% these days.
  2. Wind LCOE is 33-45% lower than it was about 3 years ago.
  3. Wind energy is the cheapest option for new electricity in many a location now.

Are you taking anything else away from this? (There are some other key benefits from these improvements…. I’ll mention them in the comments if no one else picks up on them.)
Clean Technica ( – Reproduced with permission.


  • George

    .. this presumably means a greater Merit Order Effect .. and more of the time.

  • Warwick

    Interesting article but the emphasis needs to be on LCOE rather than capacity factor. i.e. you might upgrade your project to a larger turbine choice and if the percentage increase in cost is less than the percentage gain in MWh then it would likely mean you’d make the investment. This does not necessarily mean an improved capacity factor.

    I think it would be interesting for the readers to explain how the variability in wind speeds has a significant impact on capacity factors.

    • Adam

      Adding to this, LCOE is dependent on many things and is pretty loosely tied to CF.

      There are quite a few issues with the analysis here but perhaps one take-home is the use of the term “stretch rotor” is around the fact that OEM’s are offering old turbines but putting larger blades on (simply put they’re “stretching” the rotor).

      As the blades are larger, the bending moments on the blades are higher so they can’t be placed in as windy places as WTG’s with shorter blades (see IEC WTG classes).

      Very generally speaking, this means higher capacity factors but slower wind speed sites so the gross energy is the same.

      However, because of the higher costs in these stretched rotor machines (more blade, higher mechanical loading), LCOE would go up despite CF going up too.

      This is assuming all other things being equal, but they never are. For example, if I had to guess (and it IS a guess) at the downward LCOE it’s more likely due to WTG OEM’s shifting their manufacturing bases from Europe to china (and entry of Asian suppliers to market), perhaps also global financial downturn easing commodity prices for manufacturing… but I’m starting to speculate here.

  • Concerned
    • Tim

      And with all those ups and downs, the lights are still on? Quick, call The Australian and let them know! 🙂