A higher ceiling on interest rates for consumer loans went into effect yesterday in the District of Columbia, a change that is expected to make borrowing a little easier but more expensive in coming months.

Under the terms of the law, which was approved by the D. C. City Council in November, federally insured lending institutions can charge 21 percent for direct installment loans and for car loans, compared with 15 percent before--a 40 percent jump. In addition, the law has been changed to permit banks to issue bank cards such as Visa and Master Charge.

Over the past year, banks throughout the nation have sharply curtailed consumer lending on the grounds that local usury rates made consumer loans unprofitable at a time when the cost of money was rapidly escalating. The District has been particularly affected, because its ceilings generally were lower than other areas, and local banks strongly lobbied for an increase. Maryland and Virginia also have acted in recent days to push up credit ceilings and make more credit available to consumers.

"When you get to a 13.5 percent cost of money and add in the overhead expenses, you can't make a lot of 15 percent loans and stay in business," said John Pollock, a spokesman for the D.C. Bankers Association. He said D.C. banks have continued to make commercial and foreign loans because they were not bound by the District's 15 percent rule.

Area bankers indicated yesterday that they are working now on pricing and marketing programs aimed at increasing their consumer credit business. First American Bank will have a direct-mail campaign urging consumers to consider applying for credit, according to president C. Jackson Ritchie. National Bank of Washington, a spokesman said, plans "various forms of advertising to let it be known that we are active in the market and to let customers know that money is available." The National Savings and Trust Co., within the next 90 days, will send to selected customers announcements promoting its overdraft credit program. American Security Bank expects to do limited mailings, possibly in the form of statement stuffers.

Some other banks are taking a wait-and-see attitude.

"We're glad the law came through; it's going to be an advantage for consumers and for bankers--but we haven't really decided yet on what we will do," said William Moreland, senior vice president of Riggs National Bank.

None of the bankers would say how much more consumers will have to pay for credit.

"The 15 percent lid is lifted by the law, but I don't know if banks will go immediately to the new 21 percent lid--we may go to 18 or 19 percent as an interim step," Pollock said.

Banking interests had sought a 24 percent ceiling in the District while some consumer groups pushed for an 18 percent limit. The D.C. Council compromised with the 21 percent usury rule.

The change in the District rates comes just as Maryland and Virginia move to raise their ceilings as well. State legislators in Virginia have voted to eliminate the ceiling on credit card interest rates; the ceiling now is 18 percent. Maryland lawmakers are considering a 24 percent ceiling on credit that generally has had an 18 percent cap.

Here is a summary of the ceilings on credit extended by federally insured banks and savings and loan institutions in the three jurisdictions:

Direct installment loans paid off in specific payments over a specific period of time: D.C. has a 21 percent ceiling now, compared with 15 percent before. Maryland has an 18 percent limit now, but proposed legislation would set the limit at 24 percent. Virginia now has no limit and no change has been proposed.

Revolving credit, including credit cards: D.C. has an 18 percent limit on any balance; previously, there was an 18 percent ceiling on the first $500 owed and a 12 percent ceiling thereafter. Maryland has an 18 percent limit now on the first $700 and a 12 percent limit thereafter; proposed legislation would raise the ceiling on any outstanding balance to 24 percent. Virginia now has an 18 percent limit but there will not be any limit under a measure that legislators have approved and that Gov. Charles S. Robb has said he will sign.

Motor vehicle loans: D.C. now has a 21 percent limit on car loans, compared with 15 percent previously. Maryland has a 21.5 percent limit on new-car loans, but proposed legislation would raise that to 24 percent. Virginia does not have any ceiling on new car loan limits and no change has been proposed.