AUSTIN - Those of a certain age can remember when grocery stores stocked only a few kinds of mustard.

Most people probably thought that was enough variety, but that didn't stop companies from developing new choices to compete for market share, and consumers love having choices.

A similar transformation is coming to transportation fuels, and smart energy companies are already planning for the end of oil's monopoly, according to corporate executives and academics who spoke at the University of Texas Energy Week in Austin.

"We'll now see a multi-fuel transportation sector, and the power sector is now a much more diverse set of technologies, and that diversity is increasing," said Bob Lukefahr, a co-founder of NAT-G Solutions and a veteran energy executive. "We're starting to see a dramatic shift in energy technology."

It's not as simple as eliminating fossil fuels and adopting electricity. Consumers will instead choose the right fuel for the job in an all-of-the-above market.

Pollution concerns and operating costs will drive this diversification, said Alan Lloyd, a research fellow at the UT Energy Institute who served as president of the International Council on Clean Transportation from 2006 until 2013.

"The number of mega-cities that are going to be created in the coming years means there will be continual pressure to not only reduce greenhouse gases, but also criteria pollutants (such as nitrogen and sulfur dioxides and particulates)," Lloyd said. "There will be less reliance on fossil fuels and a gradual shift to renewables, particularly solar and wind."

Engineers predict that biofuels, made from plants such as algae and sugar, will power long-range ships and aircraft, while heavy vehicles will need hydrogen fuel cells and light-duty vehicles can operate on batteries, Lloyd said.

Todd Onderdonk, a senior energy adviser for corporate strategic planning at Exxon Mobil Corp., said predicting which technologies will succeed is always a challenge. Clouding the experts' crystal balls the most, perhaps, is how efficiently we will use energy and how much cleaner we can burn fossil fuels.

"Today, the world car fleet is about 1.8 billion cars, but we see fuel economy rising from about 30 miles per gallon to about 50 miles per gallon, so you can have a lot more mobility around the world and still have the same amount of demand," he said.

New technologies can also commercialize quickly, Lukefahr pointed out.

"In 2008, there were exactly three models of cars you could purchase in the United States that got over 40 miles to the gallon in the city and on the highway. Today there are 45," he said.

Solar panel prices have fallen 70 percent since 2008 and are expected to drop another 4.4 percent in 2017, according to a report from IBISWorld, a market research firm. That kind of sudden change can also make energy companies cautious about where to invest, said Johnna Van Keuren, vice president for wind at Shell Oil Co.

"It is a different risk profile and it is a different return profile, and that's a challenge for an oil and gas company," she said. But Shell is "looking at this as a cash engine, because we believe in the next 20 to 30 years and beyond, you will need all of these different energy mixes to provide the energy resources that are going to be needed for the expanding middle class, the expansion of the population and the desire for more reliable energy resources that are clean-burning."

Major shareholders, though, can punish energy companies that diversify. Board members ousted NRG CEO David Crane because they were not happy with his attempts to develop renewable energy sources at a company that they considered a fossil fuel and nuclear power investment vehicle.

"This investor set that invests in a BP or a Shell or an NRG doesn't want that company to diversify for them. If that diversification becomes significant enough, you start getting pushback from the investor set," Lukefahr said. "The European investor tends to be much more open to that diversification than the U.S. investor does."

BP has made major investments in wind farms, ethanol and currently sells commercial jet biofuel, said Michael Liebman, senior vice president of operations at BP Wind Energy. But he agrees that a company's CEO needs investor buy-in to diversify into new forms of energy generation.

"Sit down and have meaningful conversation with your institutional investors, and decide whether they are really willing to let you drop $3 billion or $4 billion a year in capital into this, because if you're not doing that, you're not going to be competitive," he said. "It's going to be a hobby, and you're going to get embarrassed."

The future of transportation will be as diverse as today's mustard selection - which today ranges from basic yellow to balsamic, sriracha and habanero. We can choose to own a car or to summon a taxi. Sometimes we'll drive, sometimes the car will drive itself. We'll use electricity for daily commutes but have liquid-fuel vehicles to go long distance. Fleet vehicles will thrive on hydrogen.

We know global demand for energy will go up 25 percent by 2040, so the question is how to generate it cleanly. Successful energy companies want to diversify, and the trick is get their investors to allow them.