One of the families that tested the Volvo V70 plug-in hybrid.

Volvo has been among the quietest of car companies planning to offer a plug-in hybrid. But behind the scene, the company has been evaluating the Volvo V70 Plug-in Hybrid by giving the wagon to ordinary families to use for a few weeks at a time. In total, 16 families used the V70 PHEV, which provides between about 12 and 18 miles of all-electric range.

For the purposes of the evaluation, the prototype vehicles provided a button to allow test drivers, at any point, to choose between electricity or diesel engine power. It’s fascinating to learn that most drivers chose to use electricity in city traffic at lower speeds, but manually switched to diesel for highway driving. Apparently, drivers wanted to use electricity where they believed it offered the largest environmental benefit. They also stated that the driving characteristics of city driving were better suited to electric power, while diesel seemed better at higher speeds.

Volvo collected the responses from the families—all employees of Volvo or Vattenfall, the Swedish energy company—and logged data from the vehicles. Here are additional high-level findings from the research:

• Drivers felt that 12 to 18 miles was not enough all-electric range. Individual drivers called for at least 30 miles, but as much as 50 to 100 miles. Yet, the test drivers didn’t want to spend more on the plug-in Volvo 70 than for a conventional version. This desire for longer electric range but at no additional cost creates a challenge for automakers.
• Despite the desire for additional electric range, data logs showed that drivers often did not use all the available electricity in the batteries. This was attributed to frequent manual shifts to diesel power, and an adjustment to calmer driving patterns—sometimes “severe” shifts—to conserve energy.
• Charging went smoothly. None of the test drivers neglected to charge on a daily basis, or reported any problems with disruption of home electricity supply.
• One public charging station was installed for test drivers, but none of the test drivers ever used it.
• Before the testing began, some test drivers worried about how the quietness of the electric-drive vehicle could pose a danger to pedestrians. After the test, drivers said that the issue was less of a problem than expected.
• Before the test, participants cited lower carbon emissions and climate issues as a reason to invest in plug-in technology. Afterwards, they were more likely to say that improved local air quality and less noise were the critical gains.

Volvo Cars yesterday confirmed that it will manufacture a plug-in diesel hybrid diesel as early as 2012. In a company press release, Volvo claimed that its plug-in hybrid could achieve approximately 125 miles per gallon, based on the European test cycle. In a press conference at the 2010 Paris Motor Show, Stefan Jacoby, president and CEO of Volvo Cars, yesterday also said the all-electric Volvo C30 will be produced in 2011 for test fleets in Europe, China and the US.

The results of the plug-in hybrid family test program were published in a Vattenfall report, “Business Intelligence for E-Mobility.” [PDF: 1.3M]