A new study has found billions of dollars will be saved if e-cigarettes remain freely available.

The University of Otago study shows liberalising the rules around vaping products has led to a gain of 236,000 life years for the general population, and savings of $3.4 billion in the health system over their newly extended lifespans.

"This is a sizeable gain in health for the New Zealand population and also an important benefit in terms of lower health costs," said lead author Dr Frederieke Petrović-van der Deen.

The research suggested it will have the same effect on public health as 15 years of 10 percent excise tax increases.

The gains will rely on vaping products remaining cheaper than traditional cigarettes.

"At the same time it would be helpful if there was also a sinking lid on the number of outlets that sold tobacco - just like in some areas of New Zealand there is a sinking lid on poker machines as a way of reducing harm from problem gambling," said co-author Prof Nick Wilson.

"Other regulations to minimise the risks of youth uptake of vaping include bans on online marketing aimed at youth, and possible restrictions on flavours that might be particularly attractive to youth, for example the use of names like 'unicorn milk'. This is an approach that is being adopted in the United States."

According to the Ministry of Health, while safer than traditional cigarettes, vaping isn't completely harmless.

The research was published in journal Epidemiology.

Newshub.