While 20 per cent of students sat NAPLAN online this year, with every student set to sit the tests on computers by 2020, Year 12 exams across Australia are still largely delivered via pen and paper.

Victorian Curriculum and Assessment Authority chief executive Dr David Howes said it would be problematic if the power went out while 45,000 students were sitting their VCE English exam and air conditioners were “running hot”.

"It's not like we can say, 'do it again tomorrow'," he said.

“The sticking point with VCE is ensuring that no students are disadvantaged, which means ensuring that power supply is continuous."

Dr Howes comments follow the Australian Energy Market Operator warning last week that there was a one in three chance of power failure in Victoria this summer unless immediate action was taken.

There is only one online VCE exam – a critical thinking test for the extended investigations subject.

Last week, the NSW Education Standard Authority announced it would introduce a computer exam for a high-level science extension course.

The Victorian Curriculum and Assessment Authority has been trialling online testing since 2013.

"It is high stakes and the overriding concern has to be to making sure every kid is treated fairly," Dr Howes said.

Victorian Education Minister James Merlino also has a cautious approach.

"Whenever you move to an IT platform you need to be very careful," he said. "All the work that VCE students put in, to have something go wrong would not be acceptable."

Associate professor Debra Panizzon, an assessment expert from Monash University, said there were pros and cons with moving Year 12 exams online.

She said online tests provided a much richer learning experience and could include videos and simulations.

"It really provides a unique opportunity to assess those things that we can't assess with a pen-and-paper test," she said.

"You can pull up things, get them to watch a video and you can ask them a question, and if they can't answer that question you can give them a bit more information."

But Dr Panizzon said the disadvantages included the risk of power outages and the potential for students to Google answers and modify programs.

"Students are savvy and find ways around these things," she said.

Online testing can also be thrown into disarray by students forgetting their passwords, or being unable to access the test at a particular time, she said.

Dr Panizzon said it was time to have a discussion about moving Year 12 exams online.

"(Students) do most of their work electronically and it seems somewhat archaic to be sticking to a pen-and-paper format for assessment."