Interesting. Do they make profit off of the grid as well? Or no...
Solarcity makes a profit off each install they do already. Each install is cumulative, adding reliable revenue streams for 20-30 years. Kind of like subscriptions to Netflix, but each customer pays he monthly fee for 20-30 years.
Since demand is very strong in a 40 million rooftop market that has 99% of rooftops yet to be installed, Solarcity is building their company infrastructure to meet that staggering demand(in current 18 state markets). That means hiring a lot of people, building a lot of operations hubs, and constructing massive manufacturing centers unlike we've ever seen before.
That requires capital. More then current revenue can achieve. So, Solarcity has to get capital financing build the company to obtain those long term contracts. This looks like they aren't profitable, but the reality is they are growing the business to meet the seemingly endless demand. At the same time they are doubling, they are reducing all in costs per watt installed which is truly noteworthy since they are growing so rapidly.
As Solarcity reaches an infrastructure level that can handle the rate of installs its achieving with sales, then you will see a massive reversal in accounting profits. This is why Solarcity is so attractive as a long investment. Once growth slows down, they achieve big time profits and essentially will turn to big dividends for investors. Meanwhile, the stock will appreciate significantly giving opportunities for short term/medium term investment vehicle(it trading is your type of thing.)
How they make money is from each customer paying for the electricity the pv system produces. In the future, the grid utility will pay for each systems production just like any other power supplier. This will eventually replace net metering which is essentially the same thing without a direct contract with pv system owner. The truth is distributed solar over the grid is very reliable, extremely responsive and significantly cheaper then centralized power generation. Traditional Utilties know this and are fighting tooth and nail to slow down competition while they figure out a way to corner the solar market before these "new guys" do. It's like what gordon Gecko says, Solarcity and the distributed solar business is "going to eat your lunch" if you don't do something about it and slow these guys down. And that's exactly what a few big Utilties are doing right now, especially in Arizona.