For comparison purposes, I just changed the 3 x AA batteries on my outside sensor[1], the batteries lasted for 13 months (again, in outside conditions, including a very harsh winter).
I'm planning to write a post one of these days, but the gist of it is:
- attiny84 (don't even think about using an Arduino)
- DHT22 sensor (looking into SHT7x for better accuracy, but they're expensive as hell)
- TX module (I went with 433MHz because of better penetration)
I made 4 of these sensors, powered by batteries, so I can put them anywhere (within range, of course).
They send the reading every 4..7 x 8 seconds[2], both to keep the frequency clear (as required by law, I think it was 95% of the time) and as a poor man's anti packet collision.
They all report to a master RX, which is connected via USB to my server (which is always on anyway).
A small parser reads from serial USB and saves it in Mongo.
From there I can see the data in a simple webapp[3].
Oh yeah, and as a bonus, I made another thing that intercepts the outside sensor and display it on a 7 segment display[4], which looks really cool (plus I don't have to open the web page to see what's it like outside)
[1] https://twitter.com/emilburzo/status/799886284730892288
[2] https://github.com/ambient-monitoring/node/blob/master/node....
[3] http://ambient.emilburzo.com/
[4] https://www.flickr.com/photos/eaglex/30242342623/in/datepost...