user12128: I planning to add an anemometer to my small solar weather station.
I designed this system to run from a single 3.7v rechargeable battery and a solar panel so I have to calculate in more power drain.
What I don't really understand is do these anemometers consume any external power or just give out a voltage by themselves?
This one doesn't even have consumption specified:
https://www.adafruit.com/products/1733
For this Supply voltage : 5V - 24VDC:
http://www.ebay.com/itm/JL-FSX2-4-20MA-0-5V-Output-Wind-Speed-Sensor-Wind-Speed-Transmitter-Anemometer-/331521148973?hash=item4d3033482d

user11754: If it runs on electricity it definitely consumes power, its only how much the real question is. 
Since you are working with electronics I am going to assume that you have a multimeter, if you dont have one. Its about time you did, doesnt cost much and will save you a ton of time debugging. 
Nearly every multimeter has an onboard ammeter (the accuracy will be mentioned in the instructions manual). You can use this to determine the current consumed, have a look at a tutorial from sparkfun on how to do this

12128: <p>I planning to add an anemometer to my small solar weather station.
I designed this system to run from a single 3.7v rechargeable battery and a solar panel so I have to calculate in more power drain.</p>

<p>What I don't really understand is do these anemometers consume any external power or just give out a voltage by themselves?</p>

<p>This one doesn't even have consumption specified:</p>

<p><a href="https://www.adafruit.com/products/1733" rel="nofollow">https://www.adafruit.com/products/1733</a></p>

<p>For this Supply voltage : 5V - 24VDC:</p>

<p><a href="http://www.ebay.com/itm/JL-FSX2-4-20MA-0-5V-Output-Wind-Speed-Sensor-Wind-Speed-Transmitter-Anemometer-/331521148973?hash=item4d3033482d" rel="nofollow">http://www.ebay.com/itm/JL-FSX2-4-20MA-0-5V-Output-Wind-Speed-Sensor-Wind-Speed-Transmitter-Anemometer-/331521148973?hash=item4d3033482d</a></p>
 11754: <p>If it runs on electricity it definitely consumes power, its only how much the real question is. </p>

<p>Since you are working with electronics I am going to assume that you have a multimeter, if you dont have one. Its about time you did, doesnt cost much and will save you a ton of time debugging. </p>

<p>Nearly every multimeter has an onboard ammeter (the accuracy will be mentioned in the instructions manual). You can use this to determine the current consumed, have a look at a tutorial from <a href="https://learn.sparkfun.com/tutorials/how-to-use-a-multimeter/measuring-current" rel="nofollow">sparkfun</a> on how to do this</p>
