On Thursday, May 23, 2013 Sherry Wells stands near the storm shelter where she took cover when a tornado destroyed her home on Monday May 20, 2013 in Moore, Okla. Wells said she and her husband won a lottery draw to receive a government-subsidized rebate to install the storm shelter. A contractor finished work on the concrete bunker beneath the slab of their garage about three weeks before the tornado hit. AP Photo/David A. Lieb Kirk Guarnera takes a break from sorting through the rubble at his tornado-ravaged home Thursday, May 23, 2013, in Moore, Okla. A battered sign stands outside the wreckage of Plaza Towers Elementary School, where seven children were killed earlier in the week when a tornado hit Moore, Okla., Thursday, May 23, 2013. Classmates and survivors from Plaza Towers Elementary School Elizabeth Anderson, 6, left, and Rylee Pino, 6, read messages from other children in the area during a visit to Eastlake Elementary School in Moore, Okla., taken on May 22,2013. Teachers and students from Plaza Towers were there along with parents for their first reunion since the tragedy. AP Photo/Tulsa World, James Gibbard Christine Jones, center, is comforted by her cousin, Ann Worden, right, as she both smiles and wipes away the tears as she talks about looking for lost wedding rings at her tornado demolished home in Moore, Okla., Thursday, May 23, 2013. At left is Matthew Trawick, who is helping look through the rubble. (AP) - After living nearly 20 years in their one-story brick home, Sherry and Larry Wells finally won the lottery - for a state rebate on a home storm shelter, that is. A contractor finished installing the concrete bunker beneath the slab of their garage in early May. About three weeks later, the shelter saved their lives when a tornado that killed 24 people tore through their neighborhood. Should residential storm shelters be mandatory in the midst of Tornado Alley? Absolutely, says Sherry Wells, "it's the best thing ever." But not a single state currently requires them in homes. And not many communities do so either, though officials in the Oklahoma City suburb of Moore are now considering it. Despite the life-saving potential of personal storm shelters, the cost remains a deterrent. So, too, does a general resistance to government mandates in politically conservative states such as Oklahoma, where tornadoes are most prevalent. Even the director of an association of storm shelter manufacturers, based in Texas, is opposed to a storm shelter mandate for new homes. "Any time a governmental entity says 'thou shalt' and tries to take an individual decision into the public domain, it's going to get pushback, and you're also going to raise the cost of things," said Ernst Kiesling, executive director of the National Storm Shelter Association and a retired civil engineering professor Texas Tech University. The science of storm shelters has advanced considerably since Dorothy failed to make it to the tornado cellar at Aunty Em's Kansas farm in the 1938 movie the Wizard of Oz. Some shelters still are dug underground in the backyard. But they are increasingly made with specially fabricated concrete and steel doors to meet Federal Emergency Management Agency specifications. And they aren't necessarily underground. In some cases, closets or bathrooms are being fortified to double as "safe rooms" that can withstand furious winds even if the rest of the house is blown away. In 2011, Oklahoma announced the SoonerSafe incentive program, offering federally financed rebates of up to $2,000 to residents who install storm shelters. The state uses a lottery-style drawing to select rebate winners from among the thousands of online applications. Sherry Wells said she won this year. She and her husband decided to get the biggest shelter available - a vault-like box with wooden benches - at a cost of $4,800. The project was so freshly finished that the Wells hadn't even submitted their rebate forms when the tornado hit on Monday. "If it wasn't for the hand of God and the cellar, we wouldn't be here," Wells said as she sorted through the rubble of her home Thursday. A little over 3,000 residential storm shelters are registered Moore, a city of about 56,000, said community development director Elizabeth Jones. Moore Mayor Glenn Lewis wants to propose a city ordinance requiring all new homes to have storm shelters. But realistically, he said, city officials may be able to require them only in new assisted living facilities and apartment complexes because of cost concerns. Contractors will be part of the conversation with the City Council to see whether a broader requirement is possible, Lewis said. "We want to be competitive," he said. We don't want to price them out of the market. Asked at a news conference if a similar mandate might be considered statewide, Oklahoma Gov. Mary Fallin quickly shot down the suggestion. "We aren't going to require people to do anything, but if someone chooses to do that, we certainly encourage it," Fallin said. In the aftermath of a devastating tornado two years ago, the Joplin City Council in southwest Missouri considered several code and policy changes for homes but ultimately decided against a safe room requirement, City Manager Mark Rohr said. "I think there's a viewpoint that that's a personal determination to make," Rohr said. About 7,500 homes were damaged or destroyed in the May 2011 Joplin tornado. Rohr said 84 percent of homes have been rebuilt, fixed or have permits pending. While the city doesn't require safe rooms, it recommends that people "shelter in place" in the event of a storm - either in a basement, an interior closet or a safe room - rather than leaving to try to make it to one of several community storm shelters being built at Joplin schools. Some local governments have taken a partial step toward a residential storm shelter mandate. A Wichita, Kan., ordinance adopted in 1994 requires storm shelters in existing mobile home parks with at least 20 homes and in new parks with at least 10 mobile homes. A 2000 ordinance adopted in Wichita's home of Sedgwick County also required storm shelters for all new mobile home parks with space for at least 10 homes. Alabama is the only state that requires new schools to be built with safe rooms, according to the National Storm Shelter Association. But similar mandates could come in the future. Kiesling said a draft of the 2015 update for the International Building Code calls for new schools to have storm-safe areas. Many states and cities incorporate those building standards into their own laws. Although several schools in the Oklahoma City area already have safe rooms, the two elementary schools that were destroyed by Monday's tornado did not have them. Seven children died in one of those schools. Yet the question remains. If the government were to mandate safe rooms in schools or homes, would people actually use them? With a tornado visibly approaching their Moore home, 20-year-old Maritza Marin fled by vehicle with her mother, father and a younger sister. They drove several blocks away, then returned to see a neighbor's red car dumped onto what once was her bedroom. Marin said their home had no storm shelter. She likes the mayor's proposed requirement, but she's not sure she would use a storm shelter if she again found herself facing a tornado. "I think it would be good to have a shelter, but if you can run away from one, it's better," Marin said. Associated Press writers Ramit Plushnick-Masti in Moore and Jim Salter in St. Louis contributed to this report.