The soon to be delivered Chevrolet Volt comes standard with a 120 volt charging cable that will pull into just about any of the billions of 3 prong electrical outlet anywhere in the US. The charge time for an empty battery on 120 volts is approx 10 hours which is perfect for over night charging. The cost of a full charge will be around $1.50.
In most of the world 240 volt is the standard for residential buildings but in the US it is optional. This GM video shows the optional 240 volt charger that will be available for the Volt allowing owners to half charging time to approx 4 hours.
The 240-volt Voltec Charger will sell for $490 plus installation.