When the stock market had its recent conniption fit, financial experts were all over the business channels analyzing Wall Street's gyrations for everyday folks in Tennessee and elsewhere.

Invariably, they had sound advice for investors: Stay cool, and stay diversified. It's good advice, and not just for personal finances, either. Diversification ought to be one of the guiding principles for America's energy policy.

Earlier this month, the House passed legislation, with bipartisan support, that requires privately owned electric utilities to obtain at least 15 percent of their energy from greater efficiency and from renewable energy resources, such as wind, solar and biomass. Utilities would have until 2020 to meet the target.

The "renewable energy standard" is a good start toward diversifying America's energy assets. America has too many of its energy eggs in too few baskets, and the dangers of an unbalanced energy portfolio are becoming all too apparent — high gas prices, vulnerability to rogue regimes, unhealthy air and global warming.

The energy standard is a market-friendly policy that lets utilities figure out the best way to diversify, whether it's "co-firing" a coal-fired power plant with biomass or helping customers use electricity more efficiently.

Utilities that do better than the standard will accumulate credits they can sell to other utilities, which builds in incentives to innovate and to keep costs down.

The standard did not pass without a fight. A leading point of contention is that Tennessee and other Southeastern states will face higher energy costs because they are not as well-endowed with wind and other renewable resources as other states.

Consequently, the argument goes, Southeast utilities will be forced to buy credits from electricity retailers in windier parts of the country.

That argument is flawed. The Southeast, blessed with abundant forests that can be tapped for biomass production, is not as resource-poor as critics maintain. Greater competition from renewable resources will put downward pressure on natural gas prices, a benefit to homeowners and gas-dependent industries.

But the renewable energy standard is only a start. Conspicuously absent from the House bill is an overdue strengthening of motor vehicle fuel-economy standards, which the Senate included in an energy bill it passed earlier this year.

Making cars and trucks go farther on a gallon of gas is the single most important step our nation can take to reduce exposure to volatile fuel prices and cut off the flow of dollars to rogue regimes and terrorists that live off oil sales.

Greater fuel efficiency will buy time to accelerate commercialization of cleaner fuels and transportation technologies, such as cellulosic ethanol and plug-in hybrid vehicles, that will help us escape the oil dependence treadmill altogether.

When Congress returns from summer recess, lawmakers should finalize energy legislation that combines the House's renewable energy standard with the Senate's fuel-economy provision.

Like a savvy conservative investor, America must diversify its energy assets, building economic security and enhancing long-term environmental quality.