Weather station: How to save power?

Hi folks

I just build a fully functioning Arduino weather station the measures temperature, barometric pressure and humidity. The weather station has a transmitter placed outside which measures the data. The transmitter the transmit the data in to the house to a receiver that shows the data. Im using two 3.3v Arduino standalone builds. The communication between receiver and transmitter is handled by RF links. Im using a boost converter to power the RF links.

My problem is that the setup uses a lot of power. It uses one of those rectangular 9v batteries every day or so. How to save the power?

Im measuring the data every 15 minutes. In the mean time a transistor shuts down the power to the RF links and sensors.

I read something about putting the Arduino to sleep. My problem is that I dont know how to make sure that the receiver is awake while the transmitter is transmitting.

My first thought is that if you are using a 9 volt battery to run a 5 volt system then unless you have any 9 volt peripherals you are wasting four volts to start with.

You might want to consider some AA batteries, closer to the voltage you need, and a 'buck' converter to step up/down as appropriate?

Nick Gammon has an excellent piece on saving power / sleep on his site but I'm afraid at the moment you'll have to Google it.

Do use sleep mode: see Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors
With proper attention to detail, and everything powered by a couple of AA batteries, you should be able to run the sensor for a couple of years between battery changes.