That number is growing quickly. Amazon is several years — and tens of billions of dollars — into a huge push to deliver packages, shifting away from relying on large carriers like UPS. To begin the expansion, Amazon ordered 20,000 diesel Sprinter vans from Mercedes-Benz.

Through its network of contractors, Amazon now delivers more than half of its orders globally, and far more in the United States. Amazon has six times as many delivery depots now as it did in 2017, with at least 50 percent more new facilities set to open this year, according to data from MWPVL, a logistics consultancy.

That logistics boom, accelerated by the pandemic’s shift to online shopping, multiplies the challenges the company faces in meeting its pledge to reduce its climate impact. Its vow to make half of its deliveries carbon-neutral by 2030 is part of the company’s broader pledge to be net-carbon-neutral by 2040.

“Electrification of their delivery fleet is a really important part of that strategy,” said Anne Goodchild, who leads the University of Washington’s work on supply chain, logistics and freight transportation.

Delivery vans are well suited to electric propulsion because they usually travel 100 miles or under in a day, which means they don’t need large battery packs that add to the cost of electric cars. Delivery trucks are often used during the day and can be recharged overnight, and usually require less maintenance than gasoline trucks. Electric vehicles don’t have transmissions and certain other mechanical components that wear out quickly in the heavy stop-and-go typical in delivery routes.

In September 2019, when Mr. Bezos announced Amazon’s huge Rivian order — the largest ever order of electric vehicles — he positioned it as central to Amazon’s commitment to reduce its carbon footprint. At the time, he said he expected the 100,000 vans to be on the road “by 2024.”

Amazon invested at least $1.3 billion in Rivian, which Amazon says is supposed to make 10,000 vans as early as this year. Amazon also locked up exclusive rights to Rivian’s commercial vans for four years, with the right of first refusal for two years after that. The companies have been testing the vans for almost a year.