Tesla Model S and Model X cars ordered after January 15, 2017 will receive 400 kWh (kilowatt-hour) of free Supercharging credits (roughly 1,000 miles) annually on the anniversary of their delivery. We carefully considered current Supercharger usage and found that 400 kWh covers the annual long-distance driving needs of the majority of our owners. As a result, most owners will continue to enjoy the benefits of Supercharging on road trips at no additional cost. If customers travel beyond their annual credit, they will be charged a small fee to Supercharge. In North America, pricing is fixed within each state or province; overseas, pricing is fixed within each country. In most regions, Tesla owners will pay per kWh as it’s the fairest way to pay for the exact energy used. However, due to local regulations, in several regions we will charge per minute of usage instead, though we are actively working with regulators to update the rules.
I'm glad Tesla is implementing a pay-to-charge program like this, especially before Model 3 hits the road in mass numbers. I think it's a fair and reasonable system.