Policymakers are increasingly promoting the adoption of plug-in electric vehicles (PEVs) to help combat the global rise in CO₂ emissions. Despite the potential environmental benefits of PEVs, several structural, social, and cultural challenges may need to be overcome before PEVs can be widely adopted. One of these challenges is thought to be the limited availability of non-home PEV charging infrastructure, i.e. chargers at work, public and commercial locations. In reality, however, the relationship between the availability of non-home charging infrastructure and the uptake of PEVs is not currently well understood.

… Increasing the availability of PEV charging (home and public) is associated with two main social benefits. The first is to support the use of PEVs among current owners, allowing them to use their PEVs more extensively and ideally offsetting more gasoline-powered kilometers with electric-powered kilometers. The second benefit is to help promote PEV ownership in the first place. The idea is that widespread availability of PEV chargers will increase general awareness of PEV technology, increase perceptions of PEV functionality, and potentially allow for the development of green, innovative, and progressive “cultural branding”. It is this second benefit that we focus on here—the potential of public chargers to increase the uptake of PEVs by stimulating demand.

—Bailey et al.

The study collected information from a representative sample of 1,739 new vehicle buying households in Canada, with 536 from British Columbia. Respondents were asked about awareness of public charging in their region, and about their overall interest in purchasing a plug-in electric vehicle, such as a Chevrolet Volt or Nissan Leaf.

The results showed that as of 2013, when this survey data was collected, 18% of Canadian respondents reported being aware of at least one public charger. The data also showed that British Columbia’s Clean Energy Vehicle program—which installed almost 500 public chargers when the survey was conducted in 2013—was largely successful in increasing charger awareness. Almost one-third (31%) of British Columbian respondents had seen at least one public charger, compared to only 13% of respondents in the rest of Canada.

For comparison, a 2011 US survey found that 12% of respondents had seen public charging locations in their community; excluding the more aware province of BC, levels of awareness of at least one charger in the rest of Canada (13%) are very similar to those in the US. However, that awareness does not necessarily translate into increased plug-in electric vehicle interest.

To investigate the relationship between charger awareness and PEV interest they began with a bivariate test using Chi-Squared tests of association. The researchers constructed two categories representing awareness of public chargers: respondents have “perceived charger existence” if they state that they are aware of a public charger in at least one location type, and they have “perceived charger abundance” if they are aware of a public charger in at least two location types. The Simon Fraser team conducted Chi-Square tests with both variables.

They subsequently developed the investigation with binary logistic regression to control for socio-demographics and variables relating to respondent readiness for a PEV, and to see if the relationships observed in the Chi-Squared tests remained when controlling for other relevant variables.

We believe it is important that we control for respondents having prior interest in PEVs. Individuals with prior interest may be more likely to notice and remember PEV infrastructure. In other words, any significant bivariate relationship we observe between charger awareness and PEV interest might be spurious if pre-existing PEV interest is the true explanation. We thus deemed it important to add an explanatory variable to control for “pre-existing PEV interest”—that is, PEV interest that existed prior to the respondent completing the survey.

We did not directly ask this question on the survey, so we used two different questions that we believe serve as proxies for pre-existing interest. Our first proxy is a dummy variable indicating if the respondent stated that they had previously researched at least one of the following specific vehicle models: a Chevrolet Volt or a Nissan Leaf. Our second, alternate proxy is a dummy variable indicating if the respondent stated that they were “familiar” or “highly familiar” with either of these vehicle models. The survey questions specified these two relatively popular PEV models rather than refer to “electric vehicles” or “plug-in hybrid vehicles” more generally—we believe that reference to specific models would produce more reliable results.

—Bailey et al.

In multiple-regression analysis, perceived charger existence only had a statistically significant association with interest in PEV uptake when a single independent variable was used. Perceived abundance was estimated to be a significant predictor at the 95% confidence level where the team used “PEV research’” as a proxy to represent prior interest in PEVs. In contrast, perceived abundance was not estimated to be a significant predictor in models where “PEV familiarity” was a proxy for prior interest in PEVs.

In terms of PEV readiness, respondents with Level 1 (110/120-volt) charger access at home and respondents whom have previously researched PEV technology are more likely to be interested in PEVs— which also supports previous findings in Germany. In particular, Level 1 charger access seems to be a key predictor of interest in PEVs, being a significant predictor at a high significance level (99%) in all regression models. This finding suggests that policies aimed at investment in home recharge accessibility could have a greater impact on PEV adoption than those that focus on public charging infrastructure—such as subsidies for home charger installation or building regulations that require or facilitate charger installation. Development of home charging availability may be particularly effective among residents of apartment buildings and in housing situations where respondents are less likely to already have some form of home charger access.

—Bailey et al.

The study also found that future buyers are far more likely to be attracted to plug-in hybrid vehicles, such as the Chevrolet Volt, which can be powered by both gasoline and electricity.

When we account for the relevant factors, our analysis suggests that the relationship between public charger awareness and plug-in electric vehicle demand is weak or non-existent. In other words, the installation of public chargers might not be the best way to encourage growth in the electric vehicle market.

Given what we’ve seen here, it seems wise for governments to focus their money on incentives other than public electric vehicle chargers. We know that purchase rebates can spark consumer interest, and we’ve shown that home charging is important. In combination with the implementation of a Zero Emissions Vehicle mandate like California’s, these measures could be the biggest boosters of electric vehicle sales.

—Jonn Axsen

Grants provided by the Social Sciences and Humanities Research Council of Canada, and Natural Resources Canada funded this research.

Resources

• Bailey, H., Miele, A., and J. Axsen (2015) “Is awareness of public charging associated with consumer interest in plug-in electric vehicles?” Transportation Research Part D: Transport and Environment doi: 10.1016/j.trd.2015.02.001