Memory is far and away the most efficient upgrade for any laptop.
HP laptop are very energy efficient and conserve battery life.
It depends on the type of laptop you have. It is possible to upgrade the memory on most notebooks. It's also possible to add external memory.
Whats the fastest and most efficient
Cheat
unlikely most laptops CPU are soldered to the board either get a new one or send it back for an upgrade
No. The iBook has an integrated processor on its main logic board, making it impossible to upgrade processors. The same is true for most portable (laptop) computers.
The most energy efficient desktops are models which use laptop hardware.Apple advertises the Mac Mini as the most energy efficient computer.It will pretty much fit in the palm of your hand and you can get similar Windows computers.
A laptop if you want a complete computer that you can carry around (there is a CPU in a laptop)A CPU if you have a computer and want to upgrade or replace the "Central Processing Unit" which is the most expensive and complicated component.
Samsung laptop and hp laptop batteries are really good and last very long.As my laptop give minimum of 6 hours of internet browsing .
Whats the fastest and most efficient
The Inspiron 9300 laptop with Windows 7 is a great device. Your best and most affordable option is to upgrade the drivers. This way you can have the best of the best without having to buy a new computer.
The superlative of efficient is "most efficient."