understanding arduino and clock speed

Hi everybody, I am trying to design my own board to control a heating system. this is a battery powered system that has to run for at least a year on it's own. So if clock speed effects power consumption (an i know it does) then i need to understand this aspect of embedded design more clearly.

To get the thread rolling, my first question is this. Can i set an atmega 168 or 328 to use the internal 8mhz oscillator with the prescaler set to 8 to get a 1mhz clock and still use the arduino programming environment. If yes, how? i believe this change will help in the way of power consumption, but what might be the down side? Will serial communication still work for debugging purposes? i will not actually be using serial communication for the final app. just might need it for debug stage.

Timing related issues are not critical in this app. just needs to wake from power-down-mode every 5 or 10 minutes and check the temp on some DS18S20 onewire temp sensors and decide to turn heating pads on for an hour or so.

some current information i have on the project. on 3.3v 12mhz setup i'm seeing 160uA in SLEEP_MODE_PWR_DOWN mode and when awake i see around 10mA. i notice in the atmega data sheet they talk about getting down to a few micro amps in SLEEP_MODE_PWR_DOWN mode so i'm wondering how to get down to that level when asleep and hoping that the internal 8mhz clock scaled down to 1mhz will help with the awake power consumption.

here is another side question... i understand some of the memory size differences between 168 and 328 chip, but does the 168 use a little less power?

Thanks Jeff

but does the 168 use a little less power?

According to the data sheets (and this is the place to look) the 328 consumes 1mA more current than the 168. wow :o

Hi Grumpy_Mike, Thanks for the response. i just found that section in the data sheet and was also surprised.

Would you happen to know the answer to my other question regarding using the internal 8mhz oscillator with the prescaler set to 8 to get a 1mhz clock and whether or not i can still use the arduino programming environment with this set up?

Thanks Jeff