Energy Cost Assistance Act

Amends the Internal Revenue Code to allow an individual a credit against the income tax for a portion of such individual's home heating costs. Sets the amount of such credit at 50 percent of the product of such costs multiplied by the percentage by which the appropriate heating price index exceeds the consumer price index. Establishes a $250 maximum credit ($125 in the case of a married individual filing a separate return). Treats unmarried individuals living together as one taxpayer, allowing each his or her ratable share of such credit. Directs the Secretary of the Treasury to promulgate regulations applying such credit to renters and to condominium and cooperative owners. Requires reduction of the amount of such credit by ten percent of the taxpayer's adjusted gross income in excess of $25,000 ($12,500 in the case of a taxpayer for whom the maximum credit is $125).

Amends the Social Security Act to provide a comparable energy allowance of $200 per year to recipients of supplemental security income (SSI), and an energy cost assistance grant and an administrative allowance amounts to any State which distributed an energy cost assistance allowance to households receiving aid to families with dependent children. Specifies formulae for the computation of such State grant and allowance amounts. Requires annual adjustment of such grant and allowance amounts for increases in home heating costs. Denies the tax credit established by this Act to any individual receiving an energy cost assistance allowance.

Requires the Secretary to use a Residential Heating Price Index for each State and for the Nation prepared by the Secretary of Energy on a monthly basis and published in the Federal Register.