Hello, I've read conflicting information. I'm trying to make my own battery powered Arduino (really just ATMEGA328P-PU). According to Nick Gammon's very detailed analysis, he saved about 4mA by going from external crystal to internal clock, or from 15.15mA to 11.05mA. If you look at his page, it's under the heading "Using the internal clock".
Does that mean that just having an external oscillator consumes 4mA? That seems a lot! Other people say that the external oscillators don't consume that much power, and JeeLab's very power efficient design, which is reported to run for over 6 months, uses an external resonator. I didn't think resonators were that much different from oscillators in terms of power consumption.
Am I misunderstanding Gammon's results? At 4mA, a 2000mAh battery at 3.3V would last less than 1 month.