2021 has been a year of major growth for Tesla (TSLA -3.14%). The electric-car maker's vehicle deliveries have soared as the company benefits from higher production output at its factories.

Rapid growth in vehicle production and deliveries is expected to continue in the second half. But the extent of this growth is unclear, particularly as global supply and logistics constraints persist. Nevertheless, we can still peg a reasonable estimate on Tesla's third-quarter deliveries ahead of the end of the period this month.

Model X with its falcon wing doors open.

Model X. Image source: Tesla.

Strong momentum

By pretty much every measure, Tesla's growth in the first half of 2021 has been stellar. Total deliveries during the period exceeded 386,000. This is up from about 179,000 in the first half of 2020 and 320,000 in the second half of 2020.

A sharp increase in deliveries, as compared to the first half of 2020, has been fueled by increased production output at the company's vehicle factories in California and Shanghai.

Importantly, Tesla said in its second-quarter update that it ended the period with "global vehicle demand at record levels," setting Tesla up well for more strong deliveries in Q3.

Q3 vehicle-delivery estimate

Despite Tesla's clear manufacturing and sales momentum, forecasting the company's third-quarter deliveries is difficult because of the unusual supply chain and logistics environment. The global semiconductor shortage and port congestion were issues Tesla had to work "extremely hard" to navigate in Q2 -- and management said it expects these problems to persist in Q3.

For this reason, Tesla said in its second-quarter shareholder update that "component supply will have a strong influence on the rate of our delivery growth for the rest of this year."

Nevertheless, Tesla seems confident that strong year-over-year growth can persist. The company reiterated guidance for total 2021 deliveries to grow more than 50% over 2020. This implies about 364,000-plus deliveries in the second half of the year.

Ultimately, Tesla's third-quarter deliveries will likely be determined primarily by supply constraints. But if Tesla were to deliver half of its expected deliveries for the second half of 2021 in Q3, this would translate to about 182,000-plus deliveries -- up 30% from deliveries in the third quarter of 2020. Of course, if supply constraints don't have much of a negative impact on production output, deliveries could be much higher than this.

Investors will likely get to see how many vehicles Tesla delivered in Q3 by Oct. 3, as the company usually reports its quarterly vehicle deliveries within three calendar days of each quarter's close.