But how much would those prices go up? Jeff PETRASH, vice president and general counsel for the NPGA, couldn't say for sure.
"In the absence of it, I can't tell you what the figure would be, but I have no doubt that propane prices would go up in some, if not all of Michigan," he said.
Petrash said he was asked by the Michigan affiliate of the NPGA to get involved on the Line 5 issue, given its importance to the energy needs of states beyond Michigan.
The propane flowing through Line 5 that goes to the refinery in Sarnia, Canada is distributed everywhere from Canada to New England to Virginia, Petrash said.
"We're now at the national level getting engaged on this issue because it's very clear that the impact is not just Michigan, but really through a fairly large swath of the United States," he said.
Enbridge and its Line 5 pipelines that run beneath the Straits of Mackinac have taken immense flack from environmental opponents for a few years now, the latest round coming during a lively meeting of the state's Pipeline Safety Advisory Board (PSAB) last week.
But Enbridge, along with allies from various industry groups, have tried to spell out the economic impacts to Michigan and beyond if this stretch of pipe were shut off or shut down, as environmentalists demand.
Despite the seemingly overwhelming presence of opponents at the PSAB meeting, a number of pipeline defenders stood up and spoke about the pipe and how it supports the state's economy and energy needs. Those groups included the Michigan Chemistry Council, the Michigan Oil and Gas Association and the Michigan Manufacturers Association.
Also last week, a letter written by Douglas STOCKWELL of the International Union of Operating Engineers 324 appeared in The Detroit News, which defended the pipeline and dismissed the "environmental alarmists" who are waging a "nonsensical war on pipelines that would jeopardize warm homes, good jobs and economic growth -- all while offering alternatives that would actually harm the environment."
Petrash, echoing what other supporters have said, said pipelines are considered the cheapest way to move propane, compared to other modes of transportation. And Petrash did say Michigan is the largest propane-consuming state in the country.
But as to how much propane prices would specifically increase, Petrash said that's tough to project, given shifting market prices. Quoting a client, he said, "Projections of energy prices will only be correct by accident."
Brad SHAMLA, vice president of U.S. operations of liquids pipelines for Enbridge, put an estimated number on it based on previous propane shortages in the U.P. where he said propane prices rose above $5 a gallon.
Asked if the public is aware of the consequences of a shutdown, Shamla said earlier last week, "I think it's certainly something we want the public to understand."
As a comparison, residential use propane in Michigan costs around $2.033 per gallon as of Monday, according to this pricing website from the U.S. Energy Information Administration.
Enbridge officials have said Line 5 moves 55 percent of the propane used in Michigan and 65 percent of propane used in the Upper Peninsula to heat homes.
Petrash said someone could estimate the number of propane gallons that the 65 percent amounts to, find out how much it costs to move those gallons now, then compare that to the cost of transporting it by trucks or some other mode of transportation.
But he cited fluctuating market prices as something that could hamper that analysis.