Reducing power consumption of a raspberry Pi – BitWizard WIKI – [via]
The Raspberry Pi relies on a linear regulator for its 3V3 rail. This dissipates a third of the energy as heat, which is a bit of a waste, if you want to power your Pi from an battery. Our solution: Replace the linear regulator with a $2 switching regulator from ebay. We also used another regulator for the 5V power, to test powering a Pi from a car battery.
Reducing power consumption of a raspberry Pi - [Link]