Lately when stocks have traded unevenly, natural gas has kept up its pace in the plus column, even by surging over $9 last week. And I wouldn't be surprised to see prices go above $10 by the time the move is over, potentially lifting funds such as U.S. Natural Gas Fund (UNG).

What's behind the sprint in gas? It's pretty simple, really. Just the old story about supply and demand. Analysts say that the United States needs at least 10,000 megawatts of new power capacity per year to keep up with a 2% annual increase in the demand for electricity. In response, you may recall that a couple of years ago, there was a movement afoot to build a lot of new electricity plants in the United States powered by so-called "clean" coal and nuclear power. But this move hasn't worked out the way that the advocates of those two fuels had planned, as environmentalists and other special-interest groups have blocked efforts to develop these plants at every turn. It seems that coal-burning plants create a lot of carbon that must be offset in ways that are prohibitively expensive.

So instead, utilities have returned to natural gas, a clean-burning fuel that no one seems to complain about as much. Plus, it is plentiful in North America and is more popular than other alternatives like wind, solar and ocean power. Utilities are supportive of the shift to natural gas, because natural gas plants are easier to build, emit less carbon per unit of energy and generally slip under the radar. Even environmentalists know that they need to plug in their latte machines somehow, so they like this alternative power source, too. And now the latest figures suggest something like 7,800 new megawatts of gas-powered electricity came online last year, and at least 10,000 more megawatts will be lit up in each of the next 10 years.

As demand for natural gas strengthens in the next few years, you can bet that the prices will rise. Right now, though, the cost of natural gas had fallen quite a bit since the spike to $15 per million British thermal units, or BTUs, that followed Hurricane Katrina. By the middle of last year, the price rock-bottomed at $6, and now it is climbing back up.