After its Powerwall introduction, 75,000 units have already been spoken for! Pre-orders from 50,000 residential and 25,000 commercial users are worth about 800 million dollars in potential sales. That demand is about 1 1/2 year of production and delivery. The Gigafactory (not scheduled to open till 2016) would not be able to keep up with the additional current demands, that Tesla needs more Giga-facilities just for the home users.
Tesla's Battery Grabbed $800 Million in Its First Week - Bloomberg Business