Energy consumption is an important topic for us. Not only due to environmental concerns but also regarding the convenience of long battery life.
Weather Point uses the headphone interface on your mobile device, however the power drawn by Weather Point is only a fraction of the power used to drive your regular headphones.
The impedance of Weather Point at 25º C is around 400 000 Ohm. That leads to a power consumption of about 40 µW.
To put that in perspective: The iPhone 6's battery has a capacity of 6.9Wh. If that battery would only drive this 40µW load, that battery would last 136250 hours.
That’s around 15.5 years of nonstop weather measurement. Of course the power consumption of the iPhone itself is much higher than that.
However this example should show that the power drawn by Weather Point has almost no impact on your battery life.