High natural gas prices and hot weather are an expensive combination for electricity customers.

That duo has touched off a domino effect during the past couple of weeks that led to an emergency meeting at the Public Utility Commission on Thursday.

Some observers worry that the situation could be a harbinger of a rocky summer, when customers pay higher prices and some retail electricity providers go bust.

As people kicked up their air conditioners to deal with the early heat wave this month, some transmission lines became congested.

Wholesale power prices spiked as high as $3,000 per megawatt-hour in some areas of the state.

That happened just as two small electricity providers, National Power Co. and Pre-Buy Electric LLC, went out of business.

The Electric Reliability Council of Texas must switch their 23,000 customers to default providers, who are allowed to charge a high rate based partly on that wholesale price spike. Currently, that rate is 20 cents to 30 cents per kilowatt-hour.

This pattern could repeat itself.

"There are other small companies that are equally vulnerable, and these companies are likely to go under in the height of the summer when wholesale prices are at their highest," said Randy Chapman, executive director of consumer advocacy group Texas Legal Services Center.

PUC commissioners held an emergency meeting Thursday to discuss the issue. They took no action but urged default electricity providers, called the providers of last resort, to give customers a break.

Some agreed.

TXU Energy and Stream Energy will charge lower prices than the default rate for customers automatically switched to them. Direct Energy isn't planning a discount, but it will urge those customers to sign up for a cheaper pricing plan.

Experts say no one is immune from higher wholesale prices.

A few months ago, consumers could find fixed-rate electricity offers as low as 11 cents per kilowatt-hour. On Thursday, fixed-rate offers ranged from 13.3 cents to 17.9 cents.

Rising natural gas prices are pushing electricity rates up because Texas generates most of its power with natural gas plants.

Natural gas futures prices during the past couple of weeks have soared, nearly hitting $12 per million British thermal units. The last time natural gas cost that much was 2005, after Hurricane Rita.

Jim Steffes, head of Texas consumer services for Direct Energy, said it only takes a few spikes in the wholesale power market to push average prices higher and prompt retailers to nudge rates up.

"Even customers that are on fixed prices should understand that prices have moved up from where they were last Thanksgiving. So when they come to renew, and they talk to their suppliers and competitors, they're going to see different levels," he said.

And if more power companies go out of business, some people could experience the shift overnight.

Mr. Chapman, the consumer advocate, urged PUC commissioners at the meeting Thursday to raise the standards for starting a new retail electricity company.

Right now, anyone with $100,000 can become an electricity retailer. That isn't enough money for a retailer to lock in its future electricity costs.

If a retailer promises a fixed price to customers but doesn't lock in its own electricity costs, a rise in wholesale prices could cause the retailer to go bust.

"It's not just the poor folks, it's the whole residential market that runs the risk of picking a residential supplier incorrectly," said Geoffrey Gay, a utility lawyer with Lloyd Gosselink who opposes electricity deregulation.

He said it's "preposterous" to expect consumers to research each retailer's financial strength before choosing a pricing plan.