Keep your Iphone Charged during Power Outages

Be prepared for an Emergency.

First, always keep your phones and laptop batteries charged.

These should be readily available:

• Car Charger - to charge your phone via your car battery.
• USB Cord - you can plug your phone or tablet into your laptop (save power by not using the juice hungry laptop).

Also consider a backup charger such as a Mophie, or Zagg Sparq

On your phone:

• Close down all Apps including WiFi and Bluetooth.
• Turn down screen's brightness.
• Note texting uses less power than a call.

Source: 5 ways to keep your phone charged in a power outage - CNN.com: