When it comes to electric-car charging, speed is typically as important as availability.

Installing more charging stations is important, but it's generally thought that they need to charge a car as quickly as possible, to lessen any inconvenience to owners.

However, there's one place where speed just isn't that important.

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Portland International Airport recently added 42 charging stations--giving it the most of any airport in the U.S. according to Telefonix, the company that supplied them.

But instead of the 240-volt AC Level 2 stations typically seen in public installations, these PowerPost stations are 120-volt Level 1 units.

In other words, they provide the same output as a conventional domestic wall socket.

PowerPost Level 1 electric-car charging stations at Portland International Airport

PowerPost Level 1 electric-car charging stations at Portland International Airport

That increases the length of charging times, but in this particular case that may not be an issue.

This is because the stations will be located in the long-term parking area of the Portland International Airport.

So the cars that use them will be parked for days at a time--if not longer.

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Customers parking for four hours or more represent 85 percent of occupied spaces at most airports, Telefonix says.

The company says its Level 1 stations can recover the range depleted in a typical commute in four hours time, at a cost of about 75 cents to the host facility.

That should allow for a generous times allowance, even with the Level 1 stations, which should be able to charge most electric cars in 24 to 48 hours.

PowerPost Level 1 electric-car charging stations at Portland International Airport

PowerPost Level 1 electric-car charging stations at Portland International Airport

The Tesla Model S--with its large battery pack--is likely the only model currently in production that requires more than 24 hours of charging time.

At the same time, Level 1 stations are less expensive than Level 2 or DC fast-charging units, and use less electricity per station.

MORE: Electric Car Charging: The Basics You Need To Know

That allowed Portland International Airport to install more charging stations than it would have otherwise, Telefonix says.

The PowerPost stations will be free to use for both visitors and employees of the airport, according to the company.

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