More and more Australians are considering buying their groceries online - but few of them are actually doing it.

New research suggests more than five million people - nearly a third of shoppers - would consider ordering their groceries on the internet in the next year, up by more than 800,000 from 2018.

Coles and Woolworths customers are the keenest, ahead of those who shop at Aldi and IGA - neither of whom currently offer the option.

But only a small proportion of them currently do online shopping, according to Roy Morgan research published on Wednesday.

"The market is there for the taking however thus far consumers haven't been convinced by the online grocery services on offer," chief executive Michele Levine said in a statement.

"Just four per cent of grocery shoppers buy their groceries online in an average month equivalent to about 600,000 Australians."