The Amazon executive overseeing development of Rivian electric delivery vans says the company is on schedule to put 10,000 of the vans on the road next year, following months of testing in 15 cities. But according to one of the drivers involved with testing the vans, their range is more limited than what Rivian disclosed ahead of its blockbuster initial public offering earlier this month.

Rivian’s SEC filings for the IPO said the Amazon vans would have a range of between 120 miles and 150 miles depending on their size. But one driver involved in testing the vans said the range could be much less, depending on the weather. The driver who spoke to The Information said the battery drained about 40% faster than normal if the van’s heating or cooling was on.