Electric car drivers will not be rushing out to start paying more tax today, an electric vehicle advocacy organisation says.

From Monday, electric vehicle and plug-in hybrid owners will have to pay road-user charges (RUC), which are already required for diesel cars and heavy vehicles.

The changes mean EV owners will pay $76 per 1000km driven - the same as diesel vehicles.

And plug-in hybrid owners will pay $38 - down from the $42 that had been proposed - on a pre-pay basis.

An admin fee of $13.71 - or $12.44 if bought online - also applies to those buying RUC licences.

They had been exempt from the scheme since 2009. Diesel vehicle owners also pay RUC charges, while petrol vehicle owners pay towards the National Land Transport Fund (NLTF) through petrol excise taxes.

The charges for plug-in hybrids will be cheaper than initially planned after the government decided to accept an amendment proposed by the opposition.

The transport agency has allowed a two-month grace period so new users can understand the system.

Drive Electric Vehicles chair Kirsten Corson believed most EV drivers would be making the most of the amnesty period.

"From listening to different EV drivers, I don't think there's going to be a stampede to be paying more."

EV drivers were not opposed to paying charges but the new scheme meant electric vehicles were charged 23 percent more than petrol cars, despite being zero emission, she said.

"So at the moment there are different tax mechanisms, and unfortunately EVs have been put on the same rate as diesel vehicles which means that they're paying more tax than say petrol or hybrid vehicles."

Corson said a universal road user charge scheme was at least five years away.

But the Automobile Association (AA) was encouraging drivers to do "the right thing" and get on board sooner rather than later.

"The growing number of EVs and [plug-in hybrids] contribute to the upkeep of the road and so we'd encourage everybody, despite the grace period ... to start participating from the day the exemption ends on 1 April," AA chief policy and advocacy officer Simon Douglas said.

He said the system should be able to handle extra users.

"There's possibly going to be a little bit of an influx but ... the RUC system is well established and it will cope quite comfortably as EV and [plug-in hybrid] owners get on board with it."