Western Australia has rejected daylight saving in its fourth referendum on the issue in four decades.

With more than 70 per cent of the vote counted, almost 56 per cent of residents have voted no - the biggest no vote in WA's history.

Yes campaigner Matt Birney says they are bitterly disappointed with the result.

"We take some heart in the fact that nearly 500,000 people voted for us and for our campaign, but it wasn't enough. That's obviously a source of great disappointment not only to us but also to our supporters," he said.

Mr Birney says he accepts the majority's decision and believes this is it for daylight saving in WA.

"There's no doubt this can't be re-visited.

"This is the final nail in the coffin of daylight saving. In one fell swoop of democracy daylight saving has been defeated in this state."

WA Labor MP and no campaigner Andrew Waddell believes changing demographics played a big part in the result.

"The younger people were more environmentally aware than previously so that would play in our favour," he said.

"Plus the population itself is ageing and it seems that people who have gone through several cycles in their life realise that sometimes daylight saving works and sometimes it doesn't but the net effect is it's just not worth it."

WA's Electoral Commissioner, Warwick Gately, says there has been a subtle shift since the last referendum.

"When you look back to 1992 and before that the results were about 53 per cent 'no' and 47 per cent 'yes'," he said.

Last vote?

It is the fourth time the state has voted on the issue since 1975, with more than 1.3 million West Australians casting their votes.

The result follows a three-year trial of daylight saving, which began on the last Sunday in October and ended on the last Sunday in March.

Business leaders have been funding and supporting the yes case, arguing that daylight saving makes it easier to deal with companies in the eastern states during the summer months.

But rural groups have been pushing a strong no case, saying winding back the clocks by an hour causes major problems for farmers.

The Western Australian Farmers' Federation says the defeat of daylight saving in WA is a win for country people.

President Mike Norton says an overwhelming number of country people are against it.

"Even your larger rural voting areas like Bunbury, like Albany, like Geraldton, they were all very very high votes in the 'no'," he said.

"And there's only the pockets around the metropolitan area that were really supportive of the 'yes' campaign."

He says the 'yes' campaigners made a mistake relying on the younger vote.

"They believed that the younger generation were going to vote yes," he said.

"Look I don't know, from the polling that we've seen, the younger generation were pretty evenly split on the issue."

Earlier Premier Colin Barnett admitted casting a yes vote, saying daylight saving suits his lifestyle and is better for young families.

But he has ruled out holding another referendum on the issue during his time in office.

"If the vote is no, I suspect we'll have another call for a vote in 10 years time for another referendum," he said earlier.

"But I can assure people, as long as I am Premier of Western Australia, we'll not have a referendum for many years."

Queensland is the only other Australian state without daylight saving.