More than 1.5 million American households will go through the winter without heat or light, according to a study released yesterday by a consumer advocacy group.

According to the Citizen/Labor Energy Coalition, the recession, federal budget reductions and rising fuel costs will result in an increase over last winter of the number of homes without heat and the resulting risk, especially for older persons, of death from hypothermia--below-normal deep body temperature.

The coalition's estimates are based on a survey of 150 utilities in 22 states and do not include households heated by oil supplied by private fuel companies.

According to Michael Podhorzer, assistant director of the coalition, 54 percent of homes in New England are heated with oil. Since private companies supplying home heating oil are not prohibited from cutting off customers, as public utilities in many states are, the number of households that will be without heat this winter could be even higher than the estimate, Podhorzer said.

Earlier this year the coalition surveyed gas utilities and oil companies and determined that gas heating costs would increase by an average of 25 percent this winter. About 60 percent of American homes are heated by gas.

As the cost of heating homes has increased and the recession has deepened, the Reagan administration has reduced by $10 million the amount of money available for low-income energy assistance, from $1.85 billion in fiscal 1981 to $1.75 billion in the current 1982 fiscal year.

Hypothermia--defined medically as a body temperature below 95 degrees Fahrenheit--is particularly dangerous for older persons, who may be less able to resist or to recover from prolonged exposure to cold. Hypothermia is especially dangerous because its victims do not feel cold, and therefore do not realize that their bodies are not maintaining their proper temperature.

According to the National Center for Health Statistics, about 700 persons died from hypothermia and excessive cold in 1978, the most recent year for which statistics are available. Experts, however, generally agree that the number of persons who die of hypothermia is far greater, because hypothermia victims either appear to have suffered heart attacks or hypothermia sets off a chain reaction that results in death from another cause.

According to Dr. Richard Besdine, an academic geriatrician who has served as a consultant to the National Institute on Aging, the number of persons who die from hypothermia in the United States every winter ranges from "several to tens of thousands." Besdine said his estimate was speculative, although it was based in part on studies done in Great Britain and his own observations.

"There are a lot of deaths that are initiated by hypothermia, even though the victims have a normal body temperature when they die," he said.

Maintaining room temperatures at 65 degrees normally and at least 68 degrees for the susceptible elderly, wearing warm clothing including a muffler, mittens, a hat and warm socks can help prevent hypothermia, according to Besdine.