Tesla has delivered 200,000 electric cars in the US, triggering lower tax credits for future buyers.

According to Reuters, under a tax overhaul last year, tax credits are available for the first 200,000 electric vehicles an automaker sells.

It is then reduced by 50% every six months until it phases out.

From 1 January 2019, the current US$7,500 tax credit will go down to $3,750 until the middle of the year, Reuters said. 

Seekingalpha.com, a website for investors, noted Tesla had beaten GM and Nissan to the 200,000 mark in the US, although both would soon hit the threshold.

"While there's been plenty of debate about what the potential impact on EV demand will be as the tax incentives head lower - the implications are difficult to forecast with the Trump administration waiting in the wings to potentially issue new EV rules," it said.

Fuel prices are also seen having an effect on US sales of electrified vehicles.