The topic of public charging stations for electric cars isn’t necessarily well understood.

The release of Electric Vehicle Charging Equipment, a report by Pike Research on deployment of charging infrastructure, led us to wonder: When will the number of public charging stations for electric cars in the U.S. exceed the number of gas stations?

Analyst Lisa Jerram replied to our questions on the report–whose four-figure cost prevents us from reading it–with the following estimate:

“For the U.S., I tend to see estimates of around 150,000 gas stations. It varies, but that seems in the ballpark.

“If you look just at [publicly accessible charging stations] (not home or workplace units, or private units), that seems about equivalent to a retail gas station.

“Our forecasts show that the cumulative number of public charging stations would surpass 150,000 in the latter part of this decade, around 2018.”

In this case, “units” means any one charging station, whether it has single or multiple charging outlets.

Since there could be multiple units at a single location, Jerram admits her estimate is “a bit vague” on when the actual number of charging outlets–or units, or sites–would exceed the number of gas stations.

Jerram’s analysis says that while fewer than 200,000 units of electric vehicle supply equipment (EVSE) will be sold globally this year, that number will rise to almost 2.4 million a year by 2020.

That year, the report suggests, there will be 11.4 million electric-vehicle charging stations in operation worldwide.

“The industry is now trying to devise successful business models for deploying stations in public locations,” says Jerram, a senior research analyst at Pike.

And, she says, that effort “will become increasingly urgent as government funding winds down.”

How important the deployment of EVSEs is to adoption of electric cars depends on who you talk to.

Some advocates maintain that electric cars can never succeed without widespread and easily accessible public charging.

Others cite experience in a Japanese electric-car trial by Tokyo Electric Power (TEPCO) to suggest that while the presence of public charging stations increases driver confidence and miles covered in electric cars, the stations don’t actually get used a great deal.

Still others note that while the stations do get used, at least some of that usage is “opportunistic charging” that serves more to increase confidence–and take advantage of free charging, where it exists–than to provide critical range for cars that couldn’t otherwise be charged anywhere else.

Electric-car advocate Chelsea Sexton, for one, thinks it’s more important to get plug-in cars on the road.

If the cars come, she argued recently in Wired, the charging stations–which are relatively inexpensive compared to any other kind of fueling infrastructure–will inevitably follow.

How important do you think public charging stations are for plug-in electric cars?

Leave us your thoughts in the Comments below.

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This article originally appeared on Green Car Reports.