Tesla’s revenue from China last year tripled to more than $1 billion, indicating better traction in the market that could eventually become the company’s biggest. Bloomberg reports that China accounted for more than 15% of Tesla’s more than $7 billion of total revenue last year, according to a US regulatory filing. Sales from the US more than doubled to $4.2 billion. After a splashy start in the world’s most populous country in 2014, the electric-car maker faced setbacks including slow deliveries, and concerns about charging that CEO Elon Musk blamed on his local sales staff. China revenue fell by a third in 2015. To help address driving range concerns, Tesla said it would introduce converters that allow owners to power their vehicles at state-run charging points. The Palo Alto, California-based company doesn’t release vehicle sales or deliveries by country.