Sonoma County election officials say voters can make one simple change that would save taxpayers money and reduce waste paper at the same time.

Since 2011, voters have been allowed to opt out of receiving the "sample ballot," a mock-up of the real official ballot, to study before voting. So far only about 15,000 of the county's 243,796 registered voters have said they don't need the sample.

Printing and mailing each ballot costs about 75 cents, said Gloria Colter, assistant registrar of voters. That means it costs the county nearly $183,000 every election, primary and general, to send out them out, despite the fact that the sample ballots are freely available online.

"Everyone can go (online) and look up a sample ballot, but by law we have to send the book," she said.

Voters interested in opting or looking up an electronic version can visit Voters need to opt out by early April in order to avoid receiving the sample ballot before the June 3 primary election, she said.

The drive is part of Sonoma County Clerk-Recorder-Assessor William F. Rousseau's "Going Green Initiative." Rousseau also has been trying to encourage would-be voters to register online, saving paper, and to apply to vote by mail, avoiding vehicle emissions caused by driving to polling places.

Currently 160,391 Sonoma County voters are registered to vote by mail; the rest still vote in traditional in-person polling places. More than 13,000 county voters have used the online registration system since the California Secretary of State debuted it in 2012.

While opting out of receiving the sample ballot would save the county money, the office bills it primarily as a savings in paper. During the June 2012 primary, the office printed more than 312,000 sample ballots and voter information pamphlets, requiring nearly 2 million sheets of paper. That required the pulp from about 235 trees.

Other counties handle the sample ballot requirement differently, combining the sample and official ballot in one mailing, meaning having voters opt out wouldn't cause a dramatic cost savings.

"In most elections we include the voter information pamphlet with the actual ballot so there is only a slight incremental cost if the envelope is heavier because of the pamphlet being included," Napa County Assessor-Recorder-County Clerk John Tuteur said.

While he has been aggressively pushing mail-in voting — to the point where more than 90 percent of the county's 70,500 registered voters have signed up — he has made little effort to ask people to opt out of the sample ballot.

"I have not pushed the opt out because many of my colleagues find that voters who opt out forget they opted out and then call to ask for their sample ballot book," he said.