Consumer prices in the Washington metropolitan area rose 1.5 percent in October and November, matching the rate of inflation of the prior two months, the Laber Department reported yesterday.

Higher costs of purchasing, financing and maintaining homes were the principal causes of the continued upward spiral in prices, which has accelerated in the second half of 1978.

Homeownership costs jumped a startling 5 percent in the most recent two-month period, when home mortgage interest rates have exceeded 10 percent. Electricity, heating oil and natural gas costs declined because of warmer weather, which reduced consumption for heating, and because lower electricity rates are in effect for the winter.

However, Laber Department spokesmen said the overall decline of 7 percent in fuel and utility costs from the previous two-month period was not enough to offset the rises in home ownership costs, prices for new automobiles, medical care and entertainment and a resumption of inflation in supermarket prices.

Still, Washingtonians have fared somewhat better than residents of other large American cities in the past 12 months. According to the government, area consumer prices in November were 8.7 percent higher than a year earlier compared with an average 9 percent increase in all cities.

These figures are not adjusted for normal seasonal variations in prices, as is the national consumer price index. The local consumer index stood at 203.9 in November, which means that merchandise purchased for $100 in 1967 now costs $203.90.

Among the key spending sectors for average area residents:

Supermarket prices, which account for about 10 percent of every consumer dollar, rose 0.7 percent in the recent two months after declining 0.9 percent in August and September and rising sharply earlier in the year. Moderate price boosts for milk, beef, bakery products, processed fruits and vegetables and eggs were not offset by declines in fresh fruits, vegetables fish, seafood and nonalcoholic beverages. Since November 1977, grocery prices have increased 12 percent.

Restaurant bills and other food away from home rose 1.4 percent in October and November and are 8.6 percent higher than a year ago.

Significant increases were reported for tires, automobiles finance charges and auto maintenance, while new auto prices jumped 4.9 percent in the two months. Overall transportation costs, accounting for 17.5 percent of the average local consumer dollar, are up 8.6 percent from the end of 1977.

Medical care prices rose 2.5 percent and entertainment costs went up 2.7 percent-the largest increased in any two-month period this year, Apparel prices rose 1 percent.