The government's plans were announced in the state budget on Tuesday, although the actual fee is yet been determined.

Treasurer Rob Lucas said he was already negotiating with two other jurisdictions planning similar measures and talks had already been held with the federal treasurer.

He expects others to introduce similar charges over the next 12 months.

"We think it's possible, even in the middle of the pandemic to plan sensible, long-term reforms," Mr Lucas said.

"We're pretty confident that ultimately it's a no brainer.

"Long-term, you just need somebody to be prepared to put their toe in the water first.

"I'm confident in the long term, everyone will have to move down this particular path."

As the uptake of electric vehicles increases, the charge is designed to replace the loss of fuel excise, which is generally used to cover road maintenance costs.

SA plans to split the charge between a fixed component and one based on the kilometres driven.

Mr Lucas said he did not believe the charge would act as a disincentive for people considering changing to an electric car.

"Electric vehicles do not attract fuel excise and therefore make a lower contribution to the cost of maintaining our road networks," the treasurer said in his budget speech.

"The proposed road user charge will ensure road maintenance funding is sustainable into the future."

The government's decision also came after it allocated $18 million for a statewide charging network and a commitment to transition the government's own fleet to electric cars

With about 3000 electric cars on SA's roads at present, Mr Lucas said the new charge was initially expected to raise about $1 million annually.

Australian Associated Press