Tax-free shopping is moving two weeks later in August this year, and for the first time backpacks are on the list of tax-exempt items.

Texas' ninth annual sales tax holiday weekend will be Aug. 17-19, instead of the first weekend of the month, lining it up with the new Legislature-mandated first day of school.

Most public school students go back on Aug. 27 this year. Private schools are also starting later.

"From now on, the sales tax holiday will occur on the third Friday, Saturday and Sunday of August," Texas Comptroller Susan Combs said.

"The Legislature responded to parents' requests to add backpacks to the list of tax-exempt items," she said. "Backpacks can be expensive, especially for parents who have to buy them for several children. A tax break helps."

Fourteen states and Washington, D.C., hold sales tax holidays in August to help parents with back-to-school shopping.

The Texas Legislature established the tax-free shopping weekend in 1999 as a back-to-school-inspired break. New York and Florida started the trend.

Texas shoppers have saved about $336 million in state and local taxes since 1999, and Ms. Combs estimates tax savings of $52.1 million this year.

Purchases of most clothes and shoes priced under $100, and now backpacks, will be free from state and local taxes during the weekend.

This year, families with school-age children are expected to spend $563.49 on back-to-school merchandise, up 6.9 percent from last year, according to a survey to be released Wednesday by the National Retail Federation.

The trade group estimates total back-to-school spending this year will reach $18.4 billion, with clothing and accessories the largest category at $7.6 billion.

Lawmakers this year also created a tax-free shopping weekend for residents trying to save on their energy bills.

Starting next year, energy-efficient appliances will be exempt from sales tax during the three-day Memorial Day weekend.

Certain appliances with a federal "Energy Star" rating will be tax-free, including washing machines, dishwashers, ceiling fans, dehumidifiers, programmable thermostats and compact fluorescent light bulbs.

Air conditioners priced at $6,000 or less and refrigerators priced at $2,000 or less can also be purchased tax-free.