I'm configuring a new MacBook Pro 15″ 2015 and wanted to know if the processor speed affects the battery life?

  • 2.5GHz Quad-core Intel Core i7, Turbo Boost up to 3.7GHz
  • 2.8GHz Quad-core Intel Core i7, Turbo Boost up to 4.0GHz
  • 2
    What is your usage pattern going to be for the MacBook Pro? This will help to answer the question as if you are using it for light weight tasks, you will not really notice much difference but if you are pushing the processor (video rendering, virtual machines etc) then the 2.8 could use more if it is running closer to the top speed for longer periods of time.
    – Alain King
    May 28, 2015 at 14:26
  • Power consumption is quite linear with clock frequency, so the fastest CPU will consume about 10% more at full speed. May 28, 2015 at 15:58
  • Its irrelevant what I'm using it for....I simply want to know if both processors use identical power.
    – DD.
    May 28, 2015 at 18:52

2 Answers 2


performance per watt

You want to know the 'performance per watt'. In computing, performance per watt is a measure of the energy efficiency of a particular computer architecture or computer hardware. Literally, it measures the rate of computation that can be delivered by a computer for every watt of power consumed.

2.5GHz Quad-core Intel Core i7 = 21.05 pt/W

2.8GHz Quad-core Intel Core i7 = 33.4 pt/W

So, when only looking at the 'performance per watt' you would be better of with the 2.8GHz

Sources used: Wikipedia, cpuboss.com - 2.5GHz, cpuboss.com - 2.8GHz

note: not 100% sure if I picked the correct processor types.

  • 1
    It seems like he doesn't want to know the performance per watt, he wants to know wattage not power. If he jammed a sixteen core xeon into a Macbook Pro case, it has a far higher pt/w but even on low loads would drain the battery faster than an i7.
    – Lan
    May 28, 2015 at 12:12
  • Actually I just want to know the wattage.
    – DD.
    May 28, 2015 at 12:13
  • But the wattage depends on the load. To my understanding, when you expect the load to be the same on both processors you can use this number to calculate the wattage needed for that load. May 28, 2015 at 12:29

Considering two CPUs of the same generation (i.e. same die manufacturing process), I would expect the higher clock rate to induce some -perhaps small- increase in power consumption, as noted by CousinCocaine. This need not affect battery life directly, however:

  • Increased power consumption means increased heat production within the same closed space of your laptop.
  • With the higher-clocked CPU, although your CPU fan will kick in sooner (which means more energy consumption), there may be still be a slightly higher ambient temperature within the case.
  • Batteries don't like high temperatures.

Basically, what it boils down to is that modern laptops have huge batteries occupying a large proportion of the case. This results in longer battery charge duration, but reduces airflow.

Now, I do not have any actual numbers on battery life in similar laptops with different CPUs, so other factors may also be as important.

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