Heating bills could jump by 50 to 100 percent for almost half the homes in the Washington area if the Reagan administration's plan to deregulate natural gas prices next September is put into effect.

Customers of Washington Gas Light Co. could pay as much as $160 million more a year for gas under the deregulation plan, gas company officials estimate.

It costs an average of $540 a year to heat a home with gas now. The gas company estimates that average will jump to $982 next year if price controls are lifted.

Natural gas is used to heat nearly half the residences in the District of Columbia and its suburbs. Most of the gas customers are owners or renters of single-family homes.

Lifting federal controls on natural gas prices would hit owners of gas-heated houses with the same kind of staggering heating bill increases that the 1973-74 Arab oil embargo slapped on people who heat with electricity or oil.

Wholesale prices of natural gas are projected to at least double and probably triple as soon as prices are deregulated.

Home gas bills will probably go up less than that, however, because retail prices include the cost of delivering gas from producing areas and the cost of the gas company's pipelines, storage tanks and other facilities, neither of which should be affected by deregulation.

Estimates of the impact on local retail prices range from a "bare minimum of 50 percent" to a possible 100 percent. Even Washington Gas officials say they cannot calculate the cost precisely. Using figures from the American Gas Association, WGL estimated that local heating bills could jump 82 percent, according to gas company official Paul Young.

Washington Gas is opposed to the administration's plan to end all controls on natural gas prices on Sept. 30, Young said. He said the utility favors a previous plan to phase out controls over a longer period, with the final limits coming off in 1985.

Washington Gas collected about $226 million from sale of gas for home heating last year; an 82 percent increase would push the heating bill to almost $400 million.

The local gas company would get little or no extra revenue from that huge increase in bills. All the utility company does is the higher gas costs through from gas producers to consumers.

Young said phased decontrol is already doing what it was supposed to do: raising prices enough to encourage production of more gas and increase supplies. Since controls began to come off, Washington gas had been able to end a moratorium on hooking up new customers and hundreds of local users have switched to gas from oil or electric heat.

"We're achieving the desired result already," the gas company executive said. "All immediate decontrol would do is give the producers a tremendous benefit at the detriment of the consumers."

"This will screw the people Reagan said he was going to help -- the middle-class homeowner," said Brian Lederer, the District of Columbia people's counsel who represents the public on utility issues.

"Reagan can forget about fighting inflation if he does this," Lederer added. "It will have a tremendous impact on the city, draining out all these millions of dollars and giving them to the gas producers."

He predicted that many Washington residents will be unable to pay their heating bills if decontrol doubles gas prices, forcing the city to spend more money on home-heating subsidies for poor families.

There is little local utility regulators can do about the huge jump in prices, because regulations allow the gas company to pass any increases on to consumers automatically.

Consumers may be able to mitigate the impact of higher gas prices, but cannot offset a 100 percent increase, Lederer and Young agreed. Turning down thermostats, installing storm windows and insulation, and other energy conservation measures will pay for themselves more quickly if prices double.

Ironically, steps to cut gas consumption could lead to further increases in local gas rates. If customers practice conservation, Washington Gas will sell less fuel. But the cost of operating and maintaining the gas company's facilities will not go down. The gas company's overhead will increase, and its profits will fall. Because the company is allowed to earn a minimum profit on its investment in facilities, it will be entitled to a rate increase.