12-01-2014, 01:58 PM
A good question. If you are talking about using the 65W PowerBook adapter versus the 85W one, the 85W will likely use a half watt more when the laptop is running lightly loaded. If the 85W is a full generation newer (3 or 4 years), Apple might have improved the efficiency a small amount so they use about the same amount.
Power supplies run at the lowest efficiencies (70% to 75%) at under 10% loaded. I am too lazy to type out all the equations but here is an example:
the 85W is 10% loaded and running at 73% efficiency versus
the 65W is 15% loaded and running at 78% efficiency. Which uses more power?
Power supplies run at the lowest efficiencies (70% to 75%) at under 10% loaded. I am too lazy to type out all the equations but here is an example:
the 85W is 10% loaded and running at 73% efficiency versus
the 65W is 15% loaded and running at 78% efficiency. Which uses more power?