I agree with you - the current is measured in battery and it looks like energy consumption is increased by 2.4, you right. But in this case a run on 600MHz would save battery because 600MHz runs 2.4 faster 250MHz and it is 2.4 times shorter than 250MHz. However, if I set "ignore_nice_load" which in effect decreases the number of switches from 250MHz to 600MHz I definitely have around 50% increase in battery life. Some theory is needed to explain it. For a moment I start disbelieving in BQ27X00 measurements - it contradicts my experience. However, somebody reports a battery saving then he set 500MHz as a minimum frequency.