Tesla will probably start taking bitcoin again as payment for its cars.

So said company boss Elon Musk at a conference on Wednesday (July 21).

The outlook drove a sharp rally for the cryptocurrency.

It gained 8% following his comments and was holding at around $32,000 by Thursday (July 22) morning.

Tesla has a very on-off relationship with bitcoin.

Earlier this year the automaker said it would take the currency as payment, sparking a huge rally.

Less than two months later Musk reversed that, citing environmental concerns.

Bitcoin is produced by so-called 'mining', which requires banks of powerful computers, consuming vast amounts of energy.

Now Musk says he wants to confirm that the mining is at least 50% powered by renewables.

If it is, and if that percentage looks to be rising, he says Tesla will most likely soon start taking bitcoin again.