How much does the curtailment cost?

posted on June 13, 2019


End of May 2019 I have visited the U.S., where B-finder booth was open during American Wind Energy Association WINDPOWER 2019 in Houston, TX. It was a great experience for me to be there. Every evening after the fair I have’ enjoyed the city, especially the cuisine. During such Texan cuisine tourism in Houston, I realized one characteristic of my mind. After few minutes of searching for a new restaurant without any effects, I was disposed to drive back to the previous one, I knew from yesterday. I’d like to start this text with an observation like this: we like what we know and we afraid the new. Sorry for that if you feel again like during Spencer Johnson’s Who Moved My Cheese? lecture, but generally it’s true.


Movie. 1. People watching an emerge of The Waugh Drive Bridge colony of Mexican free-tailed bat in Houston, Buffalo Bayou Park. There is more than 200,000 bats under the bridge. Filmed by Miłosz.

The operational curtailment is a great mitigation tool for bats protection on wind farms (Arnett et al. 2013). Today the curtailment system is often based on the input data from the pre-construction bat and bird monitoring or is based on the operational bats activity monitoring results. Regardless of the source of the input data, a single collision is still just a random phenomenon impossible to predict. If you think differently maybe you should often play lottery. In this text I don’t call the effectiveness of the curtailments into question as the method of bats and birds protection. I would like to show the economic consequences of using it and I would like to open your mind for new solution.

Let’s calculate the annually costs of curtailment for a single wind turbine:

Input data:

  1. MW of one wind turbine: 3 MW.
  2. Capacity factor: 42% (Wiser R., Bolinger M. 2017)
  3. Curtailments annually: 4 months (120 days)
  4. Curtailments daily: 8h
  5. Energy price: $30/MWh


$$$ = 1x2x3x4x5



I wish you do such simulation for yourself based on your own input data.

In presented case, the cost of curtailment is $36,288 annually for single wind turbine. Let’s combine this cost with the average number of bats fatalities: 10 bats/turbine/year. You can see, that the costs of protection of 10 bats per year are $36,288 and the costs of protection of 1 bat are $3,629. You can notice, that the curtailments are using on projects with rather higher bat’s mortality. So put 50 bats instead of 10 bats. The cost of protection of one bat will be then $726.

During the Wind Europe Conference and Exhibition in Amsterdam, 2017, I have presented the poster “Counting instead of stopping”. The presented idea is to introduce a fair system of fees, based on the evidence of collisions instead of the curtailments. In such systems the fees are compensated by higher productivity. The ecological impact is compensated by a relocation of fees into mitigation actions.

Sensible system of fees should distinguish the common species from the rare one. The real participation of common species in all carcasses is higher than rare. Reasonable “taking” fees system will be better solution than losing $36,288 annually.

We see the money. What about bats and birds? Having a reasonable fees system you can compensate every single carcass by, for example, nesting boxes. Folks from the governmental wildlife management agencies, animals conservation and hunting agencies know better than me how to manage the population and keep the population fit. Generally it’s possible for the great majority of species.  I don’t like to write, that the operational curtailments is wrong way. For the protection of some bat and bird species and for the protection of your pocket, sometimes the curtailments should be the best solution for a long time.  You can imagine a wind project, where the number of collision is very high or many rare species die. Such project will generate higher payments for “taking”. In such case, using the curtailment instead of the fees will be better option for the operator, as well for bats and birds.

B-finder opens new chapter in the post construction bat and bird fatality monitoring. Thanks to the B-finder technology, you can control collisions in real time with high precision and transparency. B-finder system enables the wind power industry and the wildlife protection administration to introduce honest system for industry, wildlife and administration.

With B-finder system you can better control your money and the administration can better control the animals population.



B-finder CEO



  • Arnett E. B., G. D., Johnson W. P., Erickson, C. D. Hein. 2013. A synthesis of operational mitigation studies to reduce bat fatalities at wind energy facilities in North America. A report submitted to the National Renewable Energy Laboratory. Bat Conservation International. Austin, Texas, USA.
  • Wiser R., Bolinger M. 2017 Wind Technologies Market Report.