Last night Elon Musk announced that Tesla has built six fast charging stations in California that are now available to owners of the Tesla Model S—at least the higher-end models. Tesla will allow drivers to charge for free. The chargers will allow drivers to add 150-miles worth of energy to their batteries in about 30 minutes. Charging at ordinary public charging stations takes hours.

In anticipation of the announcement, we considered whether fast charging can make a difference for electric vehicle adoption. See “Will Fast Charging Make Electric Vehicles Practical?”  One concern with fast chargers is whether they make economic sense. In the case of Tesla, the stations won’t bring in any revenue directly, since Model S owners won’t have to pay to use them and no one else—not even Tesla Roadster owners—will be able to plug in to the proprietary system. Musk expects the system will make the Model S more attractive for customers, so the stations will essentially, from a business perspective, serve as a sales and marketing tool.

There’s a chance that the stations will be a substantial financial liability for Tesla, which today announced that it needs to raise more money to keep operating. Tesla claims that they will cost almost nothing to operate, since the power will come from solar panels. What’s not clear is whether that solar power is stored on-site in batteries, or whether it’s simply fed into the grid. (Tesla hasn’t yet responded to an request for this information.) If there are batteries, Tesla can avoid substantial demand charges from the utilities, since the chargers won’t need to draw large amounts of power directly from the grid. (The solar arrays don’t appear to be large enough to supply the 100 kilowatts the chargers draw—and even if they were, there would need to be another source of power at night or on cloudy days.) Without a battery, Tesla  will almost certainly need to pay the fee, which will be a continual drain on the coffers of the cash-strapped company. 

UPDATE: Tesla says that two of the six stations “are being set up to receive a stationary battery” that would allow them to avoid “any excessive demand charge.” The cost for each station, which will charge between 4 to 6 cars, ranges from $100,000 to $250,000.