The average weekly price of propane in Michigan is published on the website of the United States Energy Information Administration, or EIA, and on the website of the Michigan Public Service Commission, under the Department of Licensing and Regulatory Affairs. The State Heating Oil and Propane Program, or SHOPP, compiles this information for the State of Michigan.
The EIA provides the weekly price in dollars per gallon in a spreadsheet format that is viewable in Microsoft Excel. For example, this data shows that for the week ending on January 6, 1992, the cost of propane was 0.884 per gallon.
SHOPP provides the average cost per gallon of both propane and heating oil in chart form. It also provides the cost from the previous year for comparison.