Arduino Sleep is a small library that will add a sleep functionality to your project. You can use it instead of default delay() function to save power. It works on ATMega328, ATTiny84 and ATTiny85
Just replace delay() with sdelay() that's it.
when called sdelay(), arduino will enter a power down mode for given amount of time, reducing power consumtion significantly
#include "sdelay.h"
#define LED_PIN 13
#define BLINK_DELAY 1000
void setup() {
pinMode(LED_PIN, OUTPUT);
}
void loop() {
digitalWrite(LED_PIN, HIGH);
sdelay(BLINK_DELAY);
digitalWrite(LED_PIN, LOW);
sdelay(BLINK_DELAY);
}