When electric-car maker Tesla (TSLA -2.03%) was delivering 50,000 vehicles per year in 2015, almost no one would have believed that the company would not only be delivering 500,000 vehicles per year by 2020 but growing deliveries at rates above 50% year-over-year in 2021. But this is exactly what Tesla is doing.

With more than half of the year behind us, it's increasingly clear that Tesla will likely grow 2021 deliveries more than 50% this year -- an astounding achievement for a large company in a capital-intensive industry.

Here's a look at Tesla's staggering vehicle sales growth -- and why 50%-plus growth for 2021 is pretty much in the bag.

Model 3 interior.

Model 3. Image source: Tesla.

Soaring sales in the first half of 2021

After growing deliveries 36% in 2020, Tesla has been on fire in 2021. First-quarter deliveries grew 109% year over year and second-quarter deliveries soared 121% as the automaker lapped an easy year-ago comparison that was negatively impacted by factory shutdowns.

Highlighting the company's manufacturing prowess, Tesla produced 200,000 vehicles during Q2 alone. Even more impressively, this came as Tesla faced supply chain challenges -- namely semiconductor shortages and port congestion.

"The Tesla team, including supply chain, software development and our factories, worked extremely hard to keep production running as close to full capacity as possible," the company said in its second-quarter update.

Growth in vehicle deliveries was driven by a 169% year-over-year increase in combined Model 3 and Y deliveries. This put total Q2 deliveries for the two electric-car models at 204,081, up from about 76,000 in the year-ago quarter and approximately 180,000 in the first quarter of 2021.

The path to 800,000 deliveries

Tesla's demonstrated production capacity combined with a bullish narrative from management (global vehicle demand was at record levels going into Q3) for its vehicles sets the company up for 50%-plus growth in 2021.

To deliver about 800,000 vehicles this year, or 60% more than last year, Tesla only needs a slight increase in deliveries in the second half of 2021 compared to the first half. With 386,181 vehicles delivered in the first half of the year, only about 414,000 deliveries are needed in the second half of 2021 to hit 800,000 total deliveries. Considering that Tesla has production expected to come online in two new factories before the end of the year, 50%-plus growth -- and possibly growth as high as 60% -- in 2021 seems like it's in the bag for the automaker.