Europe's electric vehicle fleet now totals over one million vehicles on the strength of sales in the first half of 2018 that are 42% above last year's levels for the period, according to the data tracking firm EV Volumes.

Why it matters: The figure, which includes battery EVs and plug-in hybrids, is a symbolic milestone that nonetheless signals the rapid growth of the technology, albeit from a very small base.

• EVs are now 2.2% of the European market, they said.

The big picture: Via The Guardian, "Europe hit the [1 million] milestone nearly a year after China, which has a much larger car market, but ahead of the US, which is expected to reach the landmark later this year driven by the appetite for Tesla’s latest model."

• Sales in the first half of the year totaled 195,000 vehicles, according to EV Volumes.

The intrigue: They expect the continent's fleet to reach 1.35 million by year's end, but also warned that a "caveat" for high growth during the second half of the year is availability of supply.

• "Our tracking of plug-in vehicle inventory shows an average of only 4 days of supply on stock and 2 months of order back-log," their report notes.
• "Models with more than 10, 000 unfulfilled orders, each, are Hyundai Kona, VW e-Golf, Jaguar i-Pace and Nissan Leaf and obviously the Tesla Model 3, all of them BEVs."