To identify assessment criteria and acceptance for different charging options, we present the range of relevant constructs for all charging option and refuelling. In addition, special emphasis is placed on analysis of perceptions of fast charging of BEVs. As a first step, we will provide an overview of the assessments of all the different charging and refuelling options. Subsequently, we will report analyses designed to compare fast charging with other charging and refuelling options to gain a better understanding of the fast charging assessment criteria.
4.1 Assessment of charging and refuelling options
All respondents approached charging options by comparing them to their known and mostly routinized traffic behaviour. Familiar car ranges and refuelling at a gas station both seemed to be a first reference point in driving preferences. Experiences with electric mobility also played a crucial role in the acceptance of different charging options, in line with findings from previous studies [
5,
11]. Normative backgrounds were less relevant. Nevertheless, during the interviews important assessment criteria beyond range or even range anxiety were elicited.
4.1.1 Refuelling
The actual trip interruption caused by refuelling an ICEV is not recognized by most of the respondents. It is a subconscious part of traffic behaviour and its duration seems to be an accepted loss of time. Initially, it served as a benchmark for acceptance of charging for the majority of the sample, and was connected to the constructs “independency”, “flexibility” and “availability”. The number of constructs regarding refuelling elicited during the interviews was the highest for all the presented options (see Table
3). Compared to other elements, it was perceived as very “fast” and “flexible” and was associated with greater perceived mobility. It is “always available” and does not constrain the respondents in any way. They felt able to go where and when they want without having to plan anything. However, there were also drawbacks associated with refuelling ICEVs: compared to the other elements, respondents perceived it to be “dirty”, “out of fashion”, or even “obsolete”. Despite these drawbacks, respondents largely accepted it as an option that is suitable to everyone’s life and mobility requirements.
Table 3
List of constructs regarding refuelling, N = 20, Berlin
Realizable (10×) | (I am) free | Fully developed | Not time-consuming |
Fast (8×) | Acceptable | Given infrastructure | Obsolete |
Flexible (in time) (8×) | According to travel behaviour | Having sole responsibility | Out of fashion |
Unconstrained (use) (4×) | Conventional | I am not going to lose anything | Past |
(It is) mine (3×) | Cost intense | I have to do something | Permanent Mobility |
Comfortable (3×) | Does not constrain my individuality | I know what I’ve got | Private |
Harmful to the environment (3×) | Does not interrupt my mobility | Individual | Provides mobility |
Independent (3×) | Don’t have to plan my time | Keeps the possibility of being spontaneous | Public |
Always available (2×) | Don’t have to take care | Known | Regular speed |
Common (2×) | Don’t have to wait | Long range | Reliable |
Dirty (2×) | Efficient | Low start-up costs | Safe offer |
Don’t have to change routines (2×) | Everything is possible | Many possible ways to use | Societal acceptance |
Easy (2×) | Exclusive | My living room | To take care |
Everyday-life like (2×) | Expensive | My mobility stays as it is | Uniform transport |
Free (2×) | External resources | Need to take care | Use as it is |
Not constrained to a location (2×) | Fits my daily life | Not bound to supplier of electric energy | Works for everybody |
Practical (2×) | Flexible in time | Not innovative | |
Safe (technology) (2×) | For long term use | Not susceptible to vandalism | |
4.1.2 Normal charging (public)
The scope of perceptions of charging in public in specifically reserved parking spaces was substantially smaller than of the other options (see Table
4). It was mostly perceived as being “slow” and “uncomfortable”, and to require respondents “to change routines”, because it restricts individuals to remaining in specific locations. Respondents did not yet trust in the existing infrastructure. Consequently, this option was associated with uncertainty. Most of the respondents excluded this charging option as a possibility for themselves because they reported not having seen any charging stations along their route to or from work. Nevertheless, it is the most “known” charging option to the interviewees, although it did not result in many construct poles. Even after reflecting their traffic behaviour routines, the majority of respondents did not see this option as acceptable. Most of the respondents were concerned about the possibility of failing to locate charging station, or if they were to find a charging station it might be occupied. Although many of the respondents initially talked about a comprehensive charging infrastructure, it became a less important aspect after consideration of daily routines.
Table 4
List of constructs regarding normal charging in public, N = 20, Berlin
Slow (7×) | Public (2×) | Getting nowhere | Need to wait |
Realizable (4×) | Already existing | Having sole responsibility | Not constrained to a location |
Known (Conventional) | Bound to supplier of electric energy | I am not going to lose anything | Relaxed (time) |
Safe (technology) (3×) | Calms me down | Individual | Societal acceptance |
Uncomfortable (3×) | Comfortable | It is mine | Suitable for urban areas |
Environment friendly (2×) | Constrains my individuality | Many possible ways to use | Susceptible to vandalism |
Have to change routines (2×) | Dependent | My living room | Uniform transport |
Need to take care (2×) | External resources | My vehicle | |
Not flexible (in time) (2×) | Flexible (time) | Need to plan my time | |
Not practical (2×) | For long term use | Need to stay home | |
4.1.3 Normal charging (home)
The option of charging at home overnight was another highly accepted recharging method for most of the respondents (see Table
5). It was perceived as being “comfortable”, and respondents reported feeling as they “don’t have to take care of anything”. Although the interviewees perceived it to be the slowest option, the long charging duration was partially not perceived as being stressful. The time-consumption and location-constraints were evaluated ambivalently. Because home is the origin and destination of most of the trips, respondents saw it as a “natural station” because they would have to “go there anyway”, as phrased by one respondent. Charging at this “natural station” was seen as something that would naturally “happen along the way”, and was consequently not perceived as an interruption or as a loss of time. One respondent phrased a picturesque contrast of “my living room” for charging at home versus “to be visiting” for car sharing services. She associates the construct pole “my living room” with a very positive, warm, and cosy feeling, as well as with safety and privacy.
Table 5
List of constructs regarding charging at home, N = 20, Berlin
Comfortable (7×) | Relaxed in time (2×) | For long term use | Not forced |
Don’t have to take care of anything (5×) | Time-consuming (2×) | Free | Not innovative |
Slow (5×) | Unconstrained use (2×) | Happens along the way | Not susceptible to vandalism |
(It is) mine (4×) | According to travel behaviour | Have to change routines | Not time-consuming |
Constrained (to a location) (4×) | Calms me down | Having sole responsibility | One Possibility of use |
Not flexible (4×) | Cannot use other modes | I am not going to lose anything | Permanent Mobility |
Realizable (4×) | Constrains my individuality | I know what I’ve got | Private resources |
Safe (technology) (4×) | Dependent | Individual | Purely electric |
I have to do something (2×) | Does not interrupt my mobility | Low cost | Relaxed |
Known (2×) | Easy | Low range | Reliable |
Modern (2×) | Efficient | Mobilizes me | Societal acceptance |
Need to plan my time (2×) | Environment friendly | My living room | Suitable for rural areas |
Practical (3×) | Everything is possible | Need to stay home | Uniform transport |
Private (2×) | Exclusive | Need to wait | |
Real (2×) | Flexible in time | Not bound to supplier of electric energy | |
4.1.4 Inductive charging
The perception and assessment of inductive charging as an easy option of charging a BEV was mostly positive (see Table
6). It was seen as a very fast option, which does not necessitate exerting much additional effort, or having to change routines. It does not appear to require additional planning or unusual actions. Rather, it “happens along the way”, as phrased by one respondent. Other positive construct poles that were used to evaluate inductive charging were responses such as “sorcery” or “all-round carefree package”. This charging option does not appear lead to behavioural changes for respondents, and even makes refuelling stops redundant. Nevertheless, although the reception of inductive charging was largely positive, there were also some negative perceptions associated with this option. In the presented form, inductive charging presents an unsafe solution. Unsolved technical issues are associated with massive impacts on health and the environment (e.g., electromagnetic radiation). Consequently, a lot of “public resistance” is expected. Additionally, the high costs associated with the implementation of this technology also played a crucial role in its acceptance. Despite these concerns regarding safety and cost, inductive charging was the most accepted form of charging across our sample as it is perceived as almost invisible and very “comfortable”.
Table 6
List of constructs regarding inductive charging, N = 20, Berlin
Fast (6×) | Aesthetically acceptable | I don’t know what I’ve got | Public resistance |
Comfortable (5×) | All-round carefree package | I have to do something | Purely electric |
Hard to realize (5×) | Calms me down | Independent | Quick access |
Don’t have to take care of anything (4×) | Decent | Individual | Realizable |
Cost intense (high start-up costs) (3×) | Difficult | Interrupted mobility | Regular speed |
Flexible (3×) | Don’t have to wait | It is mine | Relaxed (time) |
Innovative (modern) (3×) | Don’t need to do anything | Many possible ways to use | Safe |
Constrained (to a location) (2×) | Dubious | My living room | Safe offer |
Fits my daily life (2×) | Environment friendly | My mobility stays as it is | Sorcery |
Flexible in time (2×) | Everyday-life like | My vehicle | Strange |
Happens along the way (2×) | Exclusive | No need to plan my time | Suitable for long distances of daily life |
Not constrained to a location (2×) | For long term use | Not bound to supplier of electric energy | Suitable for urban areas |
Not safe (2×) | Future | Not clear | Thrilling |
Practical (2×) | Given infrastructure | Not complicated | Unforced |
(I am) free | Hand over responsibility | Not susceptible to vandalism | Uniform transport |
According to travel behaviour | I am not going to lose anything | Public | Unknown |
4.1.5 Fast charging
For the assessment of fast charging, the factor of duration presents an important consideration (see Table
7). Half an hour of charging results in the inescapable consequence of having to change the traffic behaviour routines. Respondents were aware of this necessity, and produced both positive and negative appraisals in response. One of the respondents was unable to imagine using a fast charging station, because it would force him to “rearrange” his entire work day. This respondent was unable to think of potential ways to use the half hour required for charging in a productive manner. He was not willing to bring a laptop, documents, or other required items with him in the car to use this time to work. Although most of the interviewees did not accept the duration of charging associated with fast charging, the demand of a form of mobility that is always available led respondents to name the construct “flexibility” in response to this option. Despite the positive appraisal of the flexibility of this option, the drawbacks related to the duration of charging dominated the perceptions of this option. Respondents associated fast charging with massive changes in their daily routines, and consequently named negative construct poles such as “dependency” or “not free”. Other respondents with similar perceptions additionally associated fast charging with “not being practical” and with being “circumstantial”. The notion of availability was a crucial element for this group of respondents in their assessment of charging and refuelling options. To them, mobility seems to be requiring constant access and a lack of interruptions in use. Anything that differs from this conception of mobility appears to be an “obstacle” or “interference”.
Table 7
List of constructs regarding fast charging in public, N = 20, Berlin
Environment friendly (3×) | Calms me down | I am not going to lose anything | Not constrained to a location |
Need to take care (3×) | Constrained to a location | I need to plan my time | Not free |
Public (2×) | Dependent | Individual | Not practical |
Realizable (2×) | Does not work for everybody | Interrupts my mobility | Obstructive |
Safe (technology) (2×) | Expensive | It is mine | Purely electric |
Uncomfortable (2×) | External resources | Known | Societal acceptance |
Having sole responsibility | Fast | Modern | Static |
Aesthetically Inacceptable | Flexible (time) | My living room | Unacceptable |
All-round carefree package | Given infrastructure | My vehicle | Uniform transport |
Bound to supplier of electric energy | Have to change routines | Not clear | |
4.1.6 Battery replacement
Charging options that were perceived as being similar to normal refuelling appeared to be more acceptable to the respondents relative to other options (see Table
8). In this study, battery replacement at a gas station was seen as a familiar process as it is associated with similar durations and locations to which individuals are already accustomed. This option was mostly perceived as a “fast”, “flexible”, “modern” and “comfortable” way to charge a BEV. It was considered to be the fastest charging method, and therefore, an adequate alternative to refuelling. Respondents were generally unwilling to change their traffic behaviour routines. For them, it was important to maintain “the possibility of being spontaneous” that is an advantage of using an ICEV, as some stated. With this option, respondents felt as though they would be free to go wherever they want without having to plan for contingencies in case the battery runs low. Despite these benefits, some disadvantages were also associated with a battery exchange: although rated as “environmental friendly” by one participant, another respondent perceived it as a waste of resources – especially of lithium. Construct poles like “hard to realize” were associated with this option, reflecting the fact that this option would likely be challenging to implement. Some respondents criticised battery replacement as an approach that leads to indispensable deposit systems. One respondent even considered himself to be exposed to higher costs, because he expected an extra charge for the service of exchanging the battery. For this respondent, the higher expenses associated with this option would be unacceptable.
Table 8
List of constructs regarding battery replacement, N = 20, Berlin
Fast (8×) | Bound to supplier of electric energy | Given infrastructure | Not relaxed (time) |
Hard to realize (5×) | Constrained | Happens along the way | Not susceptible to vandalism |
Comfortable (4×) | Cost intense | I am not going to lose anything | Possibility of distant destinations |
Flexible (4×) | Dependent | I have to do something | Public |
Unconstrained use (4×) | Difficult | Forced | Purely electric |
(I am) free (2×) | Diligent | I know what I’ve got | Regular speed |
Always available (2×) | Does not constrain my individuality | Individual | Represents prejudice |
Efficient (2×) | Does not interrupt my mobility | It is mine | Restructures my life |
Modern (2×) | Don’t have to take care of anything | Keeps the possibility of being spontaneous | Safe offer |
Need to take care (2×) | Don’t have to wait | Makes me mobile | Societal acceptance |
No need to plan my time (2×) | Don’t need to do anything | Many possible ways to use | Suitable for rural areas |
Practical (2×) | Easy | Masculine | Super innovative |
Realizable (2×) | Environment friendly | My living room | Uncomfortable |
Safe (2×) | External resources | My mobility stays as it is | Uniform transport |
According to travel behaviour | Fits my daily life | My vehicle | Works for everybody |
Boring | For long term use | Not practical | |
4.1.7 Car sharing
The car sharing element was perceived both positively and negatively across the sample (see Table
9). For this option, prior experiences, particularly with free floating car sharing services played a major role in perception. Free floating car sharing presents a flexible contrast to round-trip car sharing: cars can simply be picked up on the street and do not have to be returned to a fixed station. Respondents who reported using car sharing services assessed this option through the construct “realizable”, and associated it with requiring “little efforts”. This form of mobility gave respondents a feeling of independence. However, respondents who reported either not having yet used these services or having used them only one or two times evaluated car sharing very differently: to these participants, availability did not seem to be guaranteed. One perceived obstacle was the required time to find a car. Relative to the charging options involving fixed stations, this option was perceived as insecure. For some respondents, owning a car was an important aspect of mobility culture and led to constructs such as “private – foreign”. For these respondents, this played a major role in the evaluation of car sharing. One respondent even directly stated that he prefers it “if something is owned by him”.
Table 9
List of constructs regarding car sharing, N = 20, Berlin
Realizable (8×) | Does not interrupt my mobility | Intermodal | Safe technology |
Don’t have to take care of anything (3×) | Easy | Interrupts my mobility | Slow |
Flexible (3×) | Exchangeable | Joint | Societal acceptance |
Comfortable (2×) | Expensive | Known | Suitable for urban areas |
Environment friendly (2×) | Fast | Lazy | Time-consuming |
External resources (2×) | Given infrastructure | Modern | To be visiting |
Need to take care (2×) | Hand over responsibility | Not constrained to a location | Unconstrained use |
Strange (2×) | Have to change routines | Not flexible in time | Uniform transport |
Uncomfortable (2×) | I know what I’ve got | Not susceptible to vandalism | Works for everybody |
Bound to supplier of electric energy | Independent | Provides mobility | |
Clean | Ineffective | Public | |
Cumbersomely | Innovative | Purely electric | |
4.1.8 Intermodality
The intermodal approach that consists of using a car until reaching the next public transport station to switch to the local public traffic system did not represent a positively rated charging option (see Table
10). Predominantly, the respondents who travel monomodal by car were consequently unable to imagine travelling with such inconvenient interruptions. One of the respondents mentioned that she would feel “like losing something” (e.g., “grocery bags”, “children”). Changes in travel mode were associated with the potential to lose items, which requires individuals to be careful and attentive. Most of the negative ratings of this option stem from the perception that charging at the station represents an unacceptable interruption of mobility. Thus, although this option was commonly associated with the positive perception of being “safe” and “environmental friendly”, for most of the respondents it was incompatible with established daily routines. This “hybrid” is partially associated with being for commuters from the suburbs.
Table 10
List of constructs regarding intermodality, N = 20, Berlin
Safe (technology) (3×) | Comfortable | Having sole responsibility | Not flexible |
Slow (3×) | Cumbersomely | Hybrid | Possibility of using other modes |
Environment friendly (2×) | Don’t have to change routines | Interrupts my mobility | Public |
Need to take care (2×) | Exchangeable | Known | Relaxed in time |
Realizable (2×) | Flexible in time | Modern | Societal acceptance |
(It is) mine | For long term use | Need to stay home | Suitable for urban areas |
Calms me down | Getting nowhere | Need to wait | Uncomfortable |
In the present study, the inclusion of assessments of a variety of charging and refuelling options resulted in more fine grained information about the factors that influence perceptions of mobility. A crucial factor in the constructs elicited by the respondents is prior experience with electric mobility. For current users of BEVs, the constructs relating to the need to plan both time and trips accordingly are distinct and nonnegative relative to those of respondents without experience with BEVs. One user reported that although she has to plan charging at home or at a charging station, it does not constitute an issue for her. She compared the process of adapting to the use of BEVs to the process of “adapting new routines to a new period of life, where you have to learn new patterns as well”. This respondent reported that she usually charges her BEV at home, and described it as a modern and comfortable charging method. She further reported that she found it “cool not having to go to a gas station anymore”.
In general, for respondent without experience driving electric vehicles or for those who do not have much information, charging options have to be close to their current routines to be seen as acceptable. Battery exchange as a substitute for refuelling seems to offer these respondents the flexibility to keep their mobility routines because this option is similar to their current mobility routines. Respondent with more experiences, however, are more open to adapting to electric mobility and are at least able to imagine integrating charging processes into their daily routines.
Although the prospect of waiting 30 min at a gas station was seen as unacceptable, some respondents were open to the possibility of fast charging periods if they were to be integrated with other activities such as shopping at a mall. An alternative approach of integrated charging that was also accepted was while being at home or at work with a reliable parking space.
4.2 Similarity in perception of fast charging and other charging and refuelling options
The second step of analyses involves comparing the similarity values across the sample. Since the present research focusses on fast charging facilities and the requirements of such a system, in this stage fast charging was compared to the rest of the charging and refuelling options. In the foreground the relative similarity or differences in the perception of the various options was explored. Note that similarity values are distinct from acceptance. It is possible, for example, for respondents to exhibit high similarity values for both fast and regular charging, while not accepting either charging option. Thus, in addition to exploring the acceptance of these options, we used the results of the content analysis to infer some of the major differences and similarities in perception of charging and refuelling options from a users’ perspective.
Table
11 shows the similarity values for fast charging compared to the other charging and refuelling options. Values are underlayed according to their height, such that lighter colours denote greater similarity and darker values denote lower similarity. Each column represents one respondent. The order of the elements in the left column is based on the overall average similarity given in the second column.
Table 11
Similarities of fast charging compared to other options in %, N = 20, Berlin
Consideration of the similarities between fast charging and regular charging in public spaces reveals that there are few differences between the two elements for the respondents. The average similarity is 82 %. Predominantly, respondents are not aware of differences because some of them lack the relevant experiences. Thus, their construct systems have not been modified by practical experiences and are instead based on known refuelling processes, in addition to being affected by mostly negative public constructs that have been distributed by the media. An initial scepticism is present in the perceptions of fast charging and regular charging, which stands in contrast to the well-known refuelling processes at gas stations. As a result, for most respondents a comprehensive public charging infrastructure is an initial requirement for acceptance. After taking the daily routines into account, it becomes apparent that it is not the mere amount of charging stations that results in negative perceptions. Even with fast charging, which reduces the waiting time during charging from several hours to 30 min, was not associated with a high rate of acceptance. Respondents did not see this 30 min waiting period as something that would be practical to integrate into their individual mobility routines: First, for most of the respondents, this time was perceived as wasted because they would be unable to use this time in a productive manner (e.g., to work). The acceptance of this option was lowest for public regular (AC) and fast (DC) charging stations located in areas where users could not do anything else. Most of the respondents were not willing to change their routines to adapt to waiting times. Nevertheless, this option was accepted by respondents who were able to think of a productive way to occupy their time close to the public charging station. Possible activities included things such as short shopping for fast charging, or working for regular charging periods. Second, another perceived obstacle to this option involved concerns about a fully charged BEV: specifically, participants were concerned about the possibility of blocking a charging station with a fully charged BEV, which would inconvenience others. For some respondents, the possibility of coming home in the evening and charging the car at a public fast charging station was associated with expectations of guilt at preventing someone else in need from using the charging station. However, respondents did not seem to think it would be practical to plan to relocate the car to avoid a guilty conscience.
Charging processes currently seem to require a similar process to refuelling. Most of the respondents were initially not able to think of scenarios to integrate fast charging or regular charging in their daily traffic behaviour. Therefore, both options were mainly perceived as unacceptable in terms of practicality and convenience. Additionally, other constructs have been phrased that stand for a negative perception of fast charging compared to regular charging options: fast charging was rated as being “more expensive”. To implement fast charging, it will be necessary to build an infrastructure that must be financed by both users and taxpayers. Consequently, fast charging is perceived to have a negative societal impact. Moreover, in additional to being perceived as being very expensive, fast charging is expected to lead to higher abrasion of batteries, which also increases the costs incurred by fast charging processes. In contrast, charging at home appears to be the most cost-efficient way of charging and therefore showed the highest acceptance.
Generally, the differences between AC and DC were is not obvious to the most of the respondents. For some of the respondents, these charging options were appraised equally. This equal assessment was highly negatively correlated with the acceptance of electric mobility in general. For instance, one respondent named the construct “crackbrained” to describe regular public charging stations. In his view, they are “the opposite of practical”, and he reported that he does “not understand why they have not been sabotaged yet”. Accordingly, all the other options of charging facilities were rated similar to regular public charging.
Another important factor is a lack of trust with regard to new technologies. Especially, missing experiences with high voltages lead to this distrust. One factor that likely contributes to this scepticism of charging is the fact that humans are unable to sense electricity without actually touching it. Electricity is typically associated with danger and life-threatening situations, and handling it is neither common nor routinized. In contrast, refuelling a car is common and routinized, despite the fact that gasoline is also potentially dangerous. Consequently, a lack of experience with charging leads to a reliance on publicly accessible information about charging and the familiar refuelling construct system.
After being asked about their daily mobility routines and actual their traffic behaviour, charging at origins and destinations seemed to be the most accepted option. Both charging options (regular charging in public and fast charging) were predominantly seen as an interruption of mobility that was perceived as a greater inconvenience than refuelling a car at a gas station. Thus, refuelling was perceived as being most different from fast charging. The average similarity for fast charging and regular refuelling was merely 54 %, which represents the lowest match between fast charging and the other options. This differentiation is based on various reasons. On the one hand, there are respondents that verbalize normative constructs such as “clean – dirty”, and “modern – old fashioned”. Environmental consciousness was important to some respondents. On the other hand, respondents perceived refuelling as a familiar and approved method that is used on a daily basis. Thus, trip interruptions are not recognized. In relation to other charging options, this option appears to require a comprehensive infrastructure that does not yet exist, prior to acceptance by the majority of the respondents.
Respondents saw concepts that include a plug-in charging station as very similar to one another. Whether or not respondents have previously noticed charging stations dominated their assessments, because most of the respondents do not yet have practical experiences with charging. Regular refuelling represents the main point of reference when assessing other options. Therefore, other elements are typically contrasted with this option. Battery exchange and inductive charging, which were both novel to most of the respondents, were mostly rated as acceptable alternatives to refuelling ICEVs. Although fast charging was associated with higher flexibility, when respondents started to reflect their own mobility patterns it became clear that this option was perceived as difficult to implement into daily routines. Fast charging may not always be the best option, unless it hits the benchmark and can take place within a time frame that is comparable to refuelling an ICEV.