If it hadn't been for rising taxes, Americans would have finished 1979 in a virtual draw with inflation, Commerce Department figures showed yesterday.

The Commerce Department said total personal income increased 12 percent during the year to a total of $2.0225 trillion. The increase nearly matched the rate of inflation.

At the same time, Americans' savings rate fell to a 30-year low of 4.5 percent of income.

Commerce also announced that housing starts fell 14 percent last year, although they surprisingly edged upward in December.

A total of 1,742,500 new housing units were started during the year, down from 2,020,300 in 1978. The decline was expected as a consequence of the government's actions to raise interest rates as part of its campaign to control inflation.

There was an 0.3 percent increase in December to 1,527,000, although building permits continued their downward slide, dropping 5 percent to 1,204,000 units. The figures were at seasonally adjusted annual rates.

The December figures reflect beginning liberalization by thrift institutions that had restricted loan commitments the previous two months, according to Sharon Stieber, director of economic analysis at the Federal Home Loan Mortgage Corp.

While overall income increased last year, taxes rose at a faster rate, up 15.8 percent. The result was that after-tax income increased only 8.7 percent, which trailed the inflation rate of about 13 percent.

The figures, contained in the government year-end report on personal income, illustrate how inflation slices into income in two ways, once through higher prices and again through higher taxes.

The tax increase occurs because Americans demand more income to keep pace with rising prices. But as incomes rise, Americans are automatically pushed into higher tax brackets, so that a greater share of their incomes goes for taxes.

Social Security taxes also increased significantly during 1979.

Relief from this jump into higher tax brackets could be provided in a tax reduction. However, President Carter has decided against recommending a tax cut in the 1981 budget he will send to Congress on Jan. 28.

Per capita income, after subtracting taxes, was $7,653 last year, an increase of $614 during the year. Per capita tax payments were $1.357, an increase of $175.

Americans obviously drew on their savings to maintain their living standards as the savings rate fell to 4.5 percent, the lowest rate since 1949, when it was 3.6 percent. Savings were 4.9 percent of income in 1978.

The savings rate in November was 3.3 percent, the lowest for any month since the department began keeping monthly figures in 1959.

Although the figures weren't complete, it seemed likely the savings rate fell even further in December since spending increased and savings were down.

Personal income increased 1.1 percent in December, the same as in November, when income hit the $2 trillion mark for the first time. Personal income includes income from all sources, including wages, rents, dividends and government benefits.

Income from wages and salaries increased one percent in December to a total of $1.2825 trillion. Income from those two factors was up 11.3 percent for the year.

Personal income expenditures rose $32.6 billion in December, double the $16.3 billion increase in November. Personal savings were $44.9 billion in December, down from $60.9 billion in November.

The Commerce Department said prices increased 0.6 percent in November, the last month for which its figures were complete, compared to 0.8 percent in October. The Labor Department's Consumer Price Index had recorded price increases of one percent in each of the two months.

The Commerce index showed prices increased 9.8 percent for the 12-month period ended in November, while the CPI measured the increase for the same period at 12.6 percent.

The chief reason for the difference is that the Commerce Department's implicit price deflator, as it is called, treats housing costs differently. Many experts believe the high mortgage interest rates have distorted the CPI figures, and that the Commerce figures may be more accurate.

In other economic reports yesterday:

The Federal Reserve said the nation's basic money supply, M1, fell to a seasonally adjusted average of $382.3 billion in the week ended Jan. 9, from the $383 billion the previous week. Story and tables on Page F7.

New claims for regular state unemployment benefits declined on a seasonally adjusted basis to 356,000 in the week ended Jan. 5, from 394,000 the previous week, the Labor Department said.

Business confidence in the U.S. economy stabilized in the final quarter of last year, but it remains at its lowest level since 1976, the Conference Board reported.

The measure of business confidence held at 32 in the final quarter of 1979, the same level posted in the third quarter. But this figure averaged 42 during the first half of last year.

The Federal Reserve Board said utilization of the nation's manufacturing capacity held steady at 84.4 percent in December, the same as in November. It was 2.4 percent below a year earlier, however.