Using a Unified Model of TPB, NAM, and SOBC to Investigate the Energy-Saving Behaviour of Urban Residents in Vietnam: Moderation Role of Cultural Values

Abstract

This study integrated the theory of planned behaviour (TPB), the norm activation model (NAM), and the stimulus–organism–behaviour–consequences theory (SOBC) to determine how external (subjective injunctive norm, subjective descriptive norm, and perceived behavioural control) and internal stimuli (ascription of responsibility, awareness of consequences) stimulate organisms (attitude towards energy saving and personal norms), which in turn drives behavioural responses (energy-saving intentions and behaviours) and their consequences (energy-saving habits). A sample of 1514 residents of five large cities in Vietnam and a multiple linear regression analysis were used to test the hypothesised model. The results show that external stimuli positively shaped a favourable energy-saving attitude, while internal stimuli aroused individuals’ personal norms. In addition, energy-saving intention, behaviours, and habits were serial mediators impacted by both internal and external stimuli. The results also indicate that a long-term orientation positively moderated the relationship between energy-saving intention, behaviours, and habits, but collectivism only moderated the nexus between energy-saving behaviours and habits. These findings imply that policymakers should focus on conveying information related to energy conservation among surrounding people, increasing citizens’ awareness of the consequences, personal responsibilities, moral obligations regarding saving energy, and should not neglect the informative role of cultural values in energy conservation practices.

1. Introduction

Current global warming is a great threat to human civilisation, and the main cause of this phenomenon is excessive energy consumption [1]. Despite this, the demand for energy is still increasing around the world. The sources of energy consumption are diverse; however, the residential sector is one of the most significant sources [2]. According to Nejat and Jomehzadeh [3], about 27% of the total energy consumed and 17% of the global CO₂ emissions are due to the residential sector. Therefore, reducing energy consumption in the residential sector can help to minimise the harmful impacts on the natural environment and the global climate.

Due to the issues mentioned above, scholars have put effort into researching pro-environmental behaviours, such as green consumption [4], energy consumption [5], and waste separation behaviours [6]. Previous pro-environmental studies have been based on various theories, but the TPB and NAM theories have been widely used [6,7]. The main argument of the TPB is that an individual’s willingness to take a specific behaviour is due to their personal motives (i.e., rational cognition), whereas the NAM posits that this willingness is a result of their morality (i.e., moral motives) [8]. The TPB posits that attitudes toward behaviour, subjective norms, and perceived behaviour control are the three antecedents of behavioural intention, and behavioural intention with perceived behaviour control are the two factors that directly form an individual’s behaviour [9]. For instance, in a pro-environmental area, when an individual has a favourable attitude towards energy-saving behaviours, they will have a higher likelihood of enacting such behaviours [10]. In other words, the NAM proposes that an individual’s behaviour is motivated by the ascription of responsibility, awareness of consequences, and personal norms [11]. More specifically, an individual’s behaviour is formed by their personal norms, which are identified by their level of awareness of consequences and the ascription of responsibility. Since the TPB model neglects the role of non-rational, non-cognitive, emotional, and altruistic motives in forming behaviour [8], one study integrated the TPB model with the NAM model to enrich the extant knowledge of pro-environmental behaviours [6]. The pro-environmental literature has illustrated that the integration of the TPB and NAM has been effective in exploring the predictors of energy-saving behaviours along with many other pro-environmental and pro-social behaviours [7,10]. However, some scholars argued that this integration is still not sufficiently convincing to explain pro-environmental behaviour and its consequences [9]. Firstly, the merged TPB–NAM model overlooks the role of environmental and contextual factors in decision-making processes [7]. Secondly, the integrated model of the TPB and NAM it neglects the consequences of actual behaviours [12,13], such as behavioural habits that are enacted with little deliberation or conscious awareness [13].

The stimulus–organism–behaviour–consequence (SOBC) framework is an important theory to understand the antecedents and subsequent various behaviours in environmental psychology [14]. This theory is seen as an advancement of the stimulus–organism–response theory [15] and the antecedent–behaviour–consequence theory [16]. The SOBC proposes that environmental stimuli (S), such as emotions, characteristics, and motives, drive individuals’ internal states or organisms (O). In turn, these organisms influence their behaviour (B) responses and then drive overt consequences (C). The SOBC theory provides an effective framework to explain the complex relationship between individuals and their environment. This theory also provides a more appropriate model for examining the relationship between behaviours and the consequences of these behaviours [14,17]. Thus, a recent study applied this theory to investigate interactions in different contexts [17]. However, to the best of our knowledge, SOBC has never been used in the energy-saving context. Therefore, in this study, we used the SOBC framework to strengthen the TPB–NAM integration and to clearly explain the rational, moral, and contextual aspects of energy behaviours.

Moreover, although the role of cultural values in other pro-environmental behaviours, such as green consumption [18,19] and the consumption of recycled products [17], has been recently investigated, to the best of our knowledge, the moderating roles of cultural values that enhance the transformation of energy-saving intention into actual behaviours and energy-saving behaviours into habits have not been considered in previous studies. In addition, scholars have emphasised that we still do not fully understand how cultural values encourage pro-environmental behaviours and have called for further efforts to develop a consistent theory of culture and pro-social behaviours [20,21,22]. In the present study, through the lens of the SOBC theory by Hofstede [19,23], two key cultural dimensions (collectivism and long-term orientation) work as contextual influences that moderate the relationships among energy-saving intention, behaviours, and habits.

In this study, the three variables in the TPB (subjective injunctive norms, subjective descriptive norm, and perceived behavioural control) are external stimuli, whereas the two factors in the NAM (ascription of responsibility and awareness of consequences) are internal stimuli [10]. In addition, the two most influential antecedents of behavioural intention in the TPB (attitude towards behaviour) and NAM (personal norms) serve as organisms. Behavioural responses include behavioural intentions and actual behaviours, while energy-saving habits are viewed as a consequence of energy-saving behaviours. Furthermore, based on the work by Hofstede [19], two cultural dimensions of collectivism and long-term orientation act as contextual moderators that can increase the transformation of behavioural intention into actual behaviours and actual behaviours into consequences.

In sum, the current study integrated Ajzen’s (1991) TPB and Schwartz’s (1977) NAM into the stimulus–organism–behaviour–consequences (SOBC) framework with the addition of moderators (i.e., the cultural values of collectivism and long-term orientation) to clearly explain the rational, moral, and contextual aspects of energy behaviours and habits. Specifically, this study aims to understand: (1) how external stimuli (subjective injunctive norm, subjective descriptive norm, and perceived behavioural control) stimulate the attitudes toward energy saving, which in turn influences energy-saving intention, and serially affects energy-saving behaviours and energy-saving habits; (2) how internal stimuli (ascription of responsibility and awareness of consequences) arouse personal norms, which in turn increase energy-saving intention, and serially impact energy-saving behaviours and energy-saving habits; (3) how cultural values (collectivism and long-term orientation) positively moderate the relationships among energy-saving intention, behaviours, and habits; and (4) how energy-saving intention results in energy-saving behaviours and how energy-saving behaviours lead to energy-saving habits.

This study is structured as follows. First, the existing literature on energy-saving behaviours is reviewed to formulate the hypotheses. Then, the research method used in this study is presented. Subsequently, the results from the multiple linear regression analysis are reported, followed by a discussion of the findings. Finally, the theoretical and practical implications, and limitations, are presented.

2. Literature Review

2.1. External Stimulus

Environmental factors, such as objective conditions and social and political environments that an individual cannot control, are called external stimuli [10]. In the TPB model, subjective norms reflect the social pressures for carrying out a specific behaviour [19]. Subjective norms can be divided into subjective injunctive norms (SINs) and subjective descriptive norms (SDNs) [24]. SINs refer to social approval or disapproval of a certain behaviour, while SDNs refer to the prevalence of that behaviour [20]. The TPB proposes that individuals tend to comply with the expectations and behaviours of their important persons [19]. When an individual perceives a positive expectation and approval about a behaviour from significant persons, they will have a favourable attitude towards that behaviour, and therefore increase the likelihood of performing the behaviour [25].

Similarly, perceived behavioural control (PBC) in the TPB model is also an external stimulus. PBC refers to the perception of how easy or difficult it is to adopt a specific behaviour [19]. This factor relates to some external conditions, such as the availability of facilities and time, which are free from individual control. Several prior studies have demonstrated that an individual’s perceived behaviour control positively affects their attitude towards behaviour [4,26]. When a person has perceived that performing a specific behaviour is easy, they will have a positive assessment of the outcome of that behaviour, and therefore have a positive attitude towards that behaviour.

From these above arguments, this study posits that subjective injunctive norms, subjective descriptive norms, and perceived behavioural control act as external stimuli, which positively influence attitudes toward energy-saving behaviours. With stronger subjective injunctive norms, subjective descriptive norms, and perceived behavioural control, individuals have a more favourable attitude towards energy saving. Therefore, the following hypotheses are proposed:

Hypothesis 1 (H1).

Subjective injunction norms positively stimulate attitudes toward energy-saving behaviours.

Hypothesis 2 (H2).

Subjective descriptive norms positively stimulate attitudes toward energy-saving behaviours.

Hypothesis 3 (H3).

Perceived behavioural control positively stimulates attitudes toward energy-saving behaviours.

2.2. Internal Stimulus

The two main factors of the NAM model—awareness of consequences and ascription of responsibility—can be seen as internal stimuli since the foundation of this model is an activation process for an individual’s inner moral and ethical dimensions [10]. The awareness of consequences refers to an individual’s awareness of the adverse and negative influences of not implementing pro-social actions on others or things, while the ascription of responsibility reflects a feeling of responsibility for the negative consequences of not acting pro-socially [27,28,29]. Rezaei and Safa [29] argued that when individuals are aware of the negative consequences of not adopting a behaviour for others and feel a personal responsibility because of these adverse consequences, they may feel a personal moral obligation to engage in a certain behaviour, which is known as personal norms [21]. In the energy-saving context, the higher one’s awareness of negative consequences and the higher one’s personal responsibility related to non-energy-saving behaviours is, the more likely that person will feel a higher moral obligation to engage in energy-saving behaviours. Therefore, the following hypotheses are proposed:

Hypothesis 4 (H4).

Awareness of consequences positively affects personal norms.

Hypothesis 5 (H5).

Ascription of responsibility positively affects personal norms.

2.3. Organisms and Behavioural Responses

In this study, attitudes toward energy-saving behaviours and personal norms were used as the organisms in the SOBC paradigm. It is argued that internal and external stimuli may inspire these organisms, which can influence the behaviour responses, including energy-saving intentions and behaviours.

Attitude towards behaviour is seen as the best predictor of behaviour intention in the TPB model [30]. Individuals will have higher intentions to perform a specific behaviour when their attitude towards that behaviour is favourable [20]. Prior studies have shown that attitudes toward energy saving positively affects individuals’ pro-environmental intentions, such as the intention for energy-saving behaviours at the workplace, organic food consumption, or mask-saving [7,31]. Likewise, in the NAM model, personal norms are the crucial construct that drive an individual’s adoption of pro-social behaviours. Based on the integrated TPB–NAM model, scholars illustrated that personal norms play an important role in forming energy-saving intentions [10].

From these above arguments, the following hypotheses are proposed:

Hypothesis 6 (H6).

Attitude towards behaviour positively affects energy-saving intentions.

Hypothesis 7 (H7).

Personal norms positively affect energy-saving intentions.

Although there is a gap between intention and behaviour, it is widely recognised that intention is a critical predictor of behaviour in general [30] and pro-environmental behaviours in particular [31,32]. Behavioural intention is seen as a strong internal stimulus and is often recognised as a cause of behaviour [33,34]. The theory of planned behaviour demonstrates that intention plays an important role in predicting behaviour in various areas. Environmental behaviour intention is defined as individuals’ perception engaging in pro-environmental behaviours, reflecting their propensity to take part in a particular environmental behaviour [35,36]. The prediction role of intention in pro-environmental behaviours has been proven in previous studies [37,38,39]. In an energy-saving context, the results of the relationship between energy-saving intention and behaviour are still inconsistent. While one study illustrated that energy-saving intention had a positive impact on energy-saving behaviour [33], another study showed that there was an insignificant relationship between energy-saving intention and behaviour [34]. These inconsistent results imply that further studies on this relationship are needed. Thus, the current study argues that energy-saving intention has a positive effect on energy-saving behaviour. The following hypothesis is proposed:

Hypothesis 8 (H8).

Energy-saving intention positively affects energy-saving behaviour.

2.4. Behavioural Response and Consequence

The literature on psychology has increasingly suggested that the consequence of a repeated behaviour is a habit [35]. A habit, which is a routine action that is repeatedly automatic and tends to occur subconsciously, is easily shaped by past behaviours [36]. Contemporary theory considers a habit as a behavioural tendency that tends to be enacted with little deliberate awareness, and as a consequence, it occurs quickly, efficiently, and automatically, with little effort [12,37]. Haith and Krakauer [40] also argue that habits are conceptually similar to skills, in that sequences of behaviours become automatic and natural. The roles of various antecedents, such as policy environment [22], negative and positive perceptions [41], or group values, norms, and interactions [42], in developing pro-environmental behaviours have been explored by scholars. However, little is known about how energy-saving behaviours develop energy-saving habits or the underlying mechanisms that facilitate or restrain the translation of energy-saving behaviours into habits. In other words, little attention has been paid to the sequence of energy-saving behaviours, but this information is extremely necessary not only for environmentalists but also for policymakers to enable them to protect the environment and maintain our planet. Based on the structured lens of the SOBC theory, we conceptualise energy-saving habits as a consequence of energy-saving behaviours to test how and under which conditions urban residents’ energy-saving behaviours transform into energy-saving habits. The following hypothesis is proposed:

Hypothesis 9 (H9).

Energy-saving habits are positively associated with energy-saving behaviours.

2.5. Moderation Effects

Culture is known as “the collective programming of the mind that distinguishes the member of one group or category of people from others” [40]. Six key dimensions of culture include collectivism/individualism, power distance, uncertainty avoidance, masculinity/femininity, long-term orientation, and indulgence/restraint [41]. These dimensions shape individuals’ beliefs, norms, and shared values, which in turn trigger particular behaviours [32,42,43]. Despite receiving some criticisms due to the assumption that the inhabitants of a particular country are representatives of a single national culture, scholars argued that Hofstede’s model still provides a useful conceptual foundation and roadmap for understanding human behaviour [43].

In recent studies, Hofstede’s cultural dimensions have been increasingly used to explore various pro-social behaviours, such as general environmental behaviour [44] and green consumption [45]. However, the employment of these dimensions in an energy-saving context is still limited. To the best of our knowledge, no prior studies have used these cultural dimensions as moderators that can strengthen the energy-saving intention–behaviour–habit path. Therefore, based on the integrated SOBC model, this study utilised the two most widely used cultural dimensions (collectivism and long-term orientation) [46,47] to explain pro-environmental behaviours. Specifically, this study tested whether cultural values could moderate the relationships among energy-saving intentions, behaviours, and habits.

Hofstede [42,43] defined collectivism as the degree to which individuals in a society are integrated into groups. Collectivism can also be thought of as the degree to which people feel proud, loyal, and engaged in their group [15,48,49]. In a collectivist society, individuals are often members of well-built and cohesive internal groups, such as extended families [50]. Out of unconditional loyalty in such a culture, individuals in the group are willing to assist and look after each of their members [51,52,53]. They are more likely to share their resources with other members of the same group and often show favourable attitudes towards behaviours that benefit their group and community [54]. Scholars argued that collectivism is a critical factor in sustainability because collectivist societies focus on the needs of the collective and pay attention to the effects of their actions on society and the community [15,55]. In addition, because of their values of cooperation and cohesion, collectivists show a strong connection to their social and environmental problems, and they aspire to live in harmony with the natural environment [56,57,58,59]. Therefore, under the moderation effect of collectivism, urban energy-saving intentions are more likely to be translated into actual behaviours. Moreover, the process that leads a behaviour to develop into a habit is likely to be facilitated or constrained by environmental and contextual cues [12,60], such as collectivism.

From these above arguments, the following hypothesis is proposed:

Hypothesis 10 (H10).

Collectivism positively moderates the relationships among energy-saving intention, energy-saving behaviours, and energy-saving habits. As such, these positive relationships will become stronger when the level of collectivism is high.

Long-term orientation reflects the temporal orientation of a society, showing the importance of the future in terms of values, beliefs, and attitudes towards that society [61,62]. It reflects how a society encourages and rewards future orientation behaviours, such as planning or delaying gratification, or even how a society makes sacrifices today for a better tomorrow [63]. Individuals with a long-term orientation are not inspired by temporary results but by future rewards [64]. In a long-term-oriented culture, individuals will be willing to take actions that they find inconvenient, such as turning off the lights and air-conditioner, for a better future for themselves and their community [65]. Furthermore, in the field of sustainability, previous studies have demonstrated that long-term orientation is related to attitudes toward pro-social behaviours [66], pro-environmental intentions and behaviours [67], and even promoting the translation from pro-social attitudes and intentions into actual pro-social behaviours [68].

From these above arguments, the following hypothesis is proposed:

Hypothesis 11 (H11).

Long-term orientation moderates the relationships among energy-saving intention, energy-saving behaviours, and energy-saving habits. As such, these positive relationships will become stronger when the level of long-term orientation is high. You can see the hypothesis model in Figure 1.

3. Methods

3.1. Research Context and Research Process

Currently, the amount of consumed energy in Vietnam is growing higher and higher to meet the demands of economic development and rapid population growth. The residential sector uses more energy than commercial and public services. Residential energy consumption grew rapidly by nearly 140% in 10 years from 2008 to 2018 and accounted for a third of the total energy consumption [69]. However, Vietnam is struggling with an energy shortage problem due to the lack of appropriate related policies and corresponding developed technology. The current energy demand has exceeded the domestic supply. Thus, the Vietnam government identified economical and efficient energy consumption as an important way to protect the environment and develop the national economy sustainably [70]. Based on these facts, examining the energy-saving behaviours of Vietnamese residents is meaningful.

The research process is shown in Figure 2 and is carried out through three stages: (1) building the research model and scales, (2) building the questionnaire and collecting data, and (3) analysing the data and discussion of the results.

3.2. Data Collection

This study surveyed adult residents (over 18 years old) in five cities with the largest populations in Vietnam (Hai Phong, Ha Noi, Da Nang, Ho Chi Minh City, and Can Tho). The data collection was carried out for 3 months (from May to July 2022). The process of data collection included several principles. Firstly, to decrease the selection bias, one out of every five persons who crossed central areas of the city, such as supermarkets, coffee houses, or office buildings, were asked to participate in the survey. Secondly, every participant was clearly informed that this survey only served research purposes. Thirdly, before answering the questionnaire, all the concepts included in the survey were fully explained to every participant. Finally, 1694 questionnaires were completed, but 180 responses were eliminated due to missing data. Therefore, our final sample included 1514 responses. The demographic profiles of the respondents are presented in

Table 1. Demographic profiles of respondents.

Measure	Value	Frequency	Percent
Gender	Male	723	47.8
	Female	791	52.2
Age	From 18 to 19 years old	374	24.7
	From 20 to 29 years old	521	34.4
	From 30 to 39 years old	374	24.7
	From 40 to 49 years old	155	10.2
	From 50 to 59 years old	64	4.2
	Over 60 years old	26	1.7
Educational level	High school and below	526	34.8
	University (Undergraduate)	902	59.6
	University (Postgraduate or above)	86	5.6
Income (in months)	Less than VND 15,000,000	642	42.4
	From VND 16,000,000 to 25,000,000	567	37.5
	From VND 26,000,000 to 35,000,000	181	12.0
	From VND 36,000,000 to 45,000,000	93	6.1
	Over VND 45,000,000	31	2.0
Cities	Hanoi	525	34.7
	Hai Phong	147	9.7
	Da Nang	87	5.7
	Can Tho	139	9.2
	Ho Chi Minh city	616	40.7

Note: N = 1514.

.

3.3. Measure

This study adopted all scales that have been used in prior studies and modified them to be suitable for the research context. Some reversed items were added to decrease the response bias. The measurement items of energy-saving habits were adapted from Zhang and Wang [54,55], and Wang and Lin [55]. Items measuring energy-saving behaviours were adapted from the study of Zhang and Yu [54,55], including a reversed item, “I always turn on the electricity appliances when I do not use them or when I leave home”. The energy-saving intention measurement was adopted from Zhu and Alam [47], including a reversed question, “I do not have the intention to use energy-saving appliances”. Regarding the constructs in the TPB model, the measurement items of attitude towards energy saving, subjective injunctive norms, subjective descriptive norms, and perceived behavioural control were derived from the research of Ru and Wang [28]. Finally, the measurement items of the three core constructs in the NAM model—awareness of consequences, attribution of responsibility, and personal norms—were adopted from Wang and Wang [1]. All items on the scales were scored from 1 to 5, corresponding with “strongly disagree or never” to “strongly agree or always”, respectively.

3.4. Data Analysis

This study validates the hypothetical model through a two-step process. First, the confirmatory factor analysis (CFA) was employed to test the measurement model. The structural validity which consists of convergence validity and discrimination validity was also examined in this step. After that, the multiple linear regression analysis was utilized to test the hypotheses. This analysis technique is appropriate for hypotheses with interaction impacts [56,63,64,65]. In addition, Model 4 and Model 6 of the PROCESS macro approach, with 5000 bias-corrected bootstrapping samples [57,58,66,67], were used to examine mediate and moderate effects, respectively. To ensure the reliability of the analysis results, several demographic variables, such as gender, age, educational level, and monthly income, were also controlled as covariates.

4. Results and Discussions

4.1. Reliability and Validity

Before testing the research hypotheses, CFA was performed using AMOS (Analysis of Moment Structures) software version 25.0 to examine the reliability and validity of the research constructs.

Table 2. Results of Cronbach’s Alpha and confirmatory factor analysis.

Indicator	Cronbach’s Alpha	Factor Loadings	AVE	CR
Energy-saving habit (ESH)
ESH1	0.895	0.834	0.742	0.896
ESH2		0.893
ESH3		0.856
Energy-saving behaviour (ESB)
ESB1	0.835	0.781	0.560	0.836
ESB2		0.767
ESB4		0.781
ESB5		0.733
Energy-saving intention (ESI)
ESI1	0.829	0.758	0.508	0.835
ESI2		0.778
ESI3		0.799
ESI5		0.533
ESI6		0.661
Attitude towards energy saving (AES)
AES1	0.875	0.821	0.638	0.876
AES2		0.790
AES3		0.787
AES4		0.797
Subjective injunctive norm (SIN)
SIN1	0.845	0.804	0.646	0.845
SIN2		0.812
SIN3		0.794
Subjective description norm (SDN)
SDN1	0.803	0.749	0.577	0.804
SDN2		0.768
SDN3		0.762
Perceived behavioural control (PBC)
PBC1	0.823	0.785	0.546	0.827
PBC2		0.752
PBC3		0.630
PBC4		0.777
Personal norms (PN)
PN1	0.834	0.741	0.501	0.833
PN2		0.696
PN3		0.645
PN4		0.682
PN5		0.768
Awareness of consequences (AOC)
AOC1	0.875	0.835	0.638	0.876
AOC2		0.768
AOC3		0.782
AOC4		0.808
Attribution of responsibility (AOR)
AOR1	0.874	0.814	0.634	0.874
AOR2		0.792
AOR3		0.777
AOR4		0.801
Collectivism (COL)
COL1	0.892	0.824	0.627	0.893
COL2		0.726
COL3		0.843
COL4		0.834
COL5		0.714
Long-term orientation (LTO)
LTO1	0.906	0.808	0.616	0.906
LTO2		0.763
LTO3		0.767
LTO4		0.791
LTO5		0.803
LTO6		0.778

Note: N = 1514. CR: Composite reliability. AVE: Average variance extracted.

demonstrates the final results of the confirmatory factor analysis (CFA).

First, the Cronbach’s Alpha results show that ESB6 and ESI4 (reversed items) had corrected item–total correlation values lower than the threshold value of 0.3 (0.080 and 0.095, respectively), and thus, these items were removed from the scales [52,68,69]. Next, CFA was performed to examine the reliability and validity of the scales. The initial results of the CFA illustrate acceptable fit indices: χ² (695) = 3194.110; χ²/df = 4.596; p < 0.001; GFI = 0.886; CFI = 0.930; TLI = 0.921; and RMSEA = 0.049. However, item ESB3 (“When I am in a public place, I don’t like to use air conditioners”) had a standardised regression weight value of only 0.320; therefore, this item was eliminated from the ESB scale [53]. The CFA was then performed again. The final CFA results show the excellent fit indices of the measurement model: χ² (1105) = 3763.505; χ²/df = 3.406 < 5; p < 0.001; GFI = 0.901 > 0.9; CFI = 0.943 > 0.9; TLI = 0.937 > 0.9; RMSEA = 0.040 < 0.05 [53]. Additionally, the standardised regression weights of all items were higher than 0.5 (λ > 0.5), and thus, all items were significant. Furthermore, both the reliability and discriminant validity of the constructs were confirmed since all constructs had AVE values higher than 0.5, and their CRs were higher than 0.7 (see Table 2). A heterotrait–monotrait (HTMT) analysis was also used as an additional test to confirm the discriminant validity of the constructs. The analysis results show that the discriminant validity of the constructs was verified because all HTMT values were less than the threshold value of 0.9 [54].

4.2. Results of Hypotheses Testing

The results of the multiple linear regression analysis of the coefficients are illustrated in

Table 3. Discriminant validity.

Constructs	Heterotrait–Monotrait (HTMT) Analysis
	SDN	SIN	ESH	AOC	AOR	PBC	AES	ESI	PN	ESB	COL	LTO
SDN
SIN	0.672
HB	0.551	0.360
AOC	0.533	0.331	0.403
AOR	0.588	0.331	0.412	0.787
PBC	0.754	0.509	0.561	0.623	0.634
AES	0.678	0.496	0.521	0.606	0.583	0.749
ESI	0.760	0.561	0.662	0.582	0.597	0.738	0.753
PMN	0.703	0.464	0.556	0.649	0.649	0.776	0.661	0.708
ESB	0.604	0.419	0.544	0.557	0.551	0.652	0.723	0.703	0.577
COL	0.422	0.246	0.440	0.524	0.527	0.434	0.385	0.459	0.493	0.402
LTO	0.589	0.328	0.439	0.674	0.695	0.583	0.550	0.590	0.598	0.559	0.596

Notes: N = 1514.

and

Table 4. Regression models.

Variables	Attitude towards Energy-Saving		Personal Norms		Energy-Saving Intention		Energy-Saving Behaviour		Energy-Saving Habit
	Model 1	Model 2	Model 3	Model 4	Model 5	Model 6	Model 7	Model 8	Model 9	Model 10
Constant	3.967 *** (0.067)	0.832 *** (0.101)	3.897 *** (0.066)	1.333 *** (0.104)	3.861 *** (0.064)	0.908 *** (0.092)	3.984 *** (0.067)	1.985 *** (0.109)	3.710 *** (0.080)	0.193 *** (0.133)
Standardised coefficients	β	β	β	β	β	β	β	β	β	β
Gender	−0.005 (0.029)	0.031 (0.021)	−0.051 * (0.028)	−0.040 (0.023)	−0.031 *** (0.028)	−0.012 (0.020)	0.001 (0.029)	0.015 (0.023)	−0.019 (0.080)	−0.020 (0.030)
Age	0.068 * (0.014)	−0.008 (0.010)	0.113 *** (0.013)	0.049 * (0.011)	0.129 * (0.013)	0.061 ** (0.010)	0.100 *** (0.014)	0.012 (0.011)	0.114 *** (0.016)	0.051 * (0.914)
Educational level	0.105 *** (0.026)	0.095 *** (0.019)	0.024 (0.025)	0.004 (0.020)	0.054 *** (0.025)	−0.002 (0.018)	0.047 (0.026)	0.013 (0.021)	0.101 *** (0.031)	0.063 ** (0.027)
Monthly income	−0.129 *** (0.017)	−0.078 *** (0.012)	−0.056 (0.016)	−0.022 (0.013)	−0.095 *** (0.016)	−0.019 (0.011)	−0.090 ** (0.017)	−0.034 (0.013)	0.089 ** (0.020)	−0.042 (0.017)
Subjective injunctive norm		0.099 *** (0.021)
Subjective descriptive norm		0.250 *** (0.026)
Perceived behavioural control		0.435 *** (0.025)
Ascription of responsibility				0.321 *** (0.029)
Awareness of consequence				0.324 *** (0.029)
Attitude towards energy-saving						0.451 *** (0.021)
Personal norms						0.329 *** (0.022)
Energy-saving intention								0.308 *** (0.042)
Energy-saving behaviour										0.153 *** (0.049)
Collectivism x Energy-saving intention								0.030 (0.005)
Long-term orientation x Energy-saving intention								0.294 *** (0.007)
Collectivism x Energy-saving behaviour										0.139 ** (0.008)
Long-term orientation x Energy-saving behaviour										0.265 *** (0.006)
R2	0.023	0.475	0.014	0.362	0.019	0.487	0.013	0.368	0.023	0.283
Adjusted R2	0.020	0.473	0.011	0.359	0.017	0.485	0.010	0.365	0.021	0.279

Notes: N = 1514, results are based on trimmed scales. The figures in parentheses are standard errors. * p < 0.05. ** p < 0.01. *** p < 0.001.

. This analysis technique is appropriate for hypotheses with interaction impacts [55]. To ensure the reliability of the analysis results, several demographic variables, such as gender, age, educational level, and monthly income, were controlled as covariates. Table 4 illustrates the analysis results for the direct and interaction effects, while

Table 5. Mediation analyses.

Mediation Regression Coefficient Paths									Effects	BootSE	Bootstrap 95% CIs
											LLCI	ULCI
ESI	→	ESB	→	ESH					0.1514	0.0266	0.1012	0.2047
AES	→	ESI	→	ESB					0.2018	0.0233	0.1558	0.2475
AES	→	ESI	→	ESB	→	ESH			0.0418	0.0103	0.0236	0.0639
PN	→	ESI	→	ESB					0.2784	0.0292	0.2210	0.3365
PN	→	ESI	→	ESB	→	ESH			0.0566	0.0135	0.0316	0.0850
SIN	→	AES	→	ESI					0.1953	0.0256	0.1441	0.2452
SIN	→	AES	→	ESI	→	ESB			0.0627	0.0107	0.0431	0.0849
SIN	→	AES	→	ESI	→	ESB	→	ESH	0.0129	0.0035	0.0069	0.0206
SDN	→	AES	→	ESI					0.2271	0.0238	0.1811	0.2741
SDN	→	AES	→	ESI	→	ESB			0.0644	0.0110	0.0442	0.0871
SDN	→	AES	→	ESI	→	ESB	→	ESH	0.0122	0.0037	0.0060	0.0205
PBC	→	AES	→	ESI					0.2603	0.0246	0.2113	0.3079
PBC	→	AES	→	ESI	→	ESB			0.0724	0.0112	0.0514	0.0953
PBC	→	AES	→	ESI	→	ESB	→	ESH	0.0131	0.0039	0.0063	0.0215
AOR	→	PN	→	ESI					0.2401	0.0242	0.1935	0.2881
AOR	→	PN	→	ESI	→	ESB			0.1032	0.0149	0.0757	0.1335
AOR	→	PN	→	ESI	→	ESB	→	ESH	0.0210	0.0057	0.0110	0.0333
AOC	→	PN	→	ESI					0.2465	0.0254	0.1963	0.2976
AOC	→	PN	→	ESI	→	ESB			0.1059	0.0152	0.0775	0.1372
AOC	→	PN	→	ESI	→	ESB	→	ESH	0.0218	0.0059	0.0115	0.0347

Note: N = 1514, results are based on trimmed scales. LLCI: Lower level of confidence interval. ULCI: Upper level of confidence interval. SE: Standard errors.

presents the mediation analysis results using Model 4 and Model 6 of the PROCESS macro approach, with 5000 bias-corrected bootstrapping samples [56]. The empirical results also presented in Figure 3, Figure 4 and Figure 5 in the follows.

The results of the analysis show that all the external stimuli (subjective injunctive norms, subjective descriptive norms, and perceived behavioural control) were positively and significantly correlated with attitude towards energy saving (β = 0.099, 0.250, and 0.435, respectively, all with p < 0.001), while all the internal stimuli (ascription of responsibility and awareness of consequence) were positively and significantly correlated with personal norms (β = 0.321 and 0.324, respectively, all with p < 0.001). H1, H2, H3, H4, and H5 are thus supported. This finding is suitable with the high collectivist society context in Vietnam where individuals’ attitudes are strongly effected by others [44]. Additionally, it illustrates that Vietnamese urban residents are aware that not taking energy-saving behaviour may lead to bad consequences for others and they feel that they are responsible for these bad results.

In addition, the results show that two organisms (attitude towards energy-saving behaviour and personal norms) positively impacted energy-saving intention (β = 0.452 and 0.329, respectively, all with p < 0.001). Energy-saving intention also positively influenced energy-saving behaviours (β = 0.308; p < 0.001), and energy-saving behaviours positively shaped energy-saving habits (β = 0.153; p < 0.001). Thus, H6, H7, H8, and H9 are supported by the data.

More importantly, the analysis results illustrate that long-term orientation positively moderated the relationships among energy-saving intentions, behaviours, and habits (β = 0.294 and 0.265, respectively, all with p < 0.001), while collectivism only moderated the effect of energy-saving behaviours and energy-saving habits (β = 0.139, p-value < 0.01). Therefore, H10 is partially supported, while H11 is fully supported. Figure 2, Figure 3 and Figure 4 present the plots of significant interactions. The slopes of the interaction plot in Figure 2 indicate that variations in energy-saving intentions are more strongly correlated with energy-saving behaviours under the conditions of a high degree of long-term orientation. Similarly, Figure 3 and Figure 4 suggest that variations in energy-saving behaviours are more strongly correlated with energy-saving habits under the conditions of a higher degree of collectivism and long-term orientation. In other words, when residents perceived a higher degree of long-term orientation or higher level of collectivism, the likelihood of transforming their energy-saving intentions into actual behaviours and their energy-saving behaviours into habits became stronger. Although this study is the first to examine the moderation role of cultural values on the relationships among energy-saving intentions, behaviours, and habits, this finding is consistent with some studies on other pro-social behaviours, such as environmental commitment or organic food consumption [32,46,57]. It also sheds light on the fact that in a collectivist society, such as Vietnam or China, where residents respect traditional values, pride, faithfulness, and a willingness to sacrifice temporary benefits for a better tomorrow, they tend to translate their pro-environmental intentions into actual behaviours, and pro-environmental behaviours into habits, including energy-saving practices, to protect the environment and develop sustainably [32,42,44,46].

Interestingly, our mediation analyses (see Table 5) show that all the external and internal stimuli had serial multiple mediation effects on energy-saving behaviours and energy-saving habits as all the mediation regression coefficients were statistically significant (all bootstrapped 95% confidence intervals do not contain zero). These findings suggest that the integration of the external and internal psychological constructs of a “rational” model (TPB) with an “emotional” model (NAM) in the SOBC paradigm are more than sufficient to explain individuals’ energy-saving practices. In this unified framework, the three psychological constructs of the TPB and the two psychological constructs of the NAM serve as stimuli, directly arousing organisms (attitudes toward energy saving and personal norms, respectively). This in turn affects behavioural responses (energy-saving intention and behaviours), and then develops the consequence of behaviours (energy-saving habits). In line with the integrated TPB–NAM model, previous studies showed that the approval and expectations perceived by surrounding others (i.e., family members and friends), perception of the ease of saving energy, and perception of moral obligation are directly related to energy-saving intentions [20] and/or energy-saving behaviours [22,38]. However, no prior studies have considered these constructs as stimuli that can drive the energy-saving behaviours and habits underlining the complex mediation mechanism of the SOBC model.

5. Conclusions

Energy-saving behaviour is seen as an effective way to address climate change issues [22,60,61]. Therefore, researching energy-saving behaviour or habits is attracting more attention. Energy-saving behaviour is relatively complex, depending on both individual and contextual factors [62]. However, scholars have emphasised that we still do not fully understand how cultural values encourage pro-environmental behaviours in general and energy-saving behaviour in particular, and have called for further efforts to develop a consistent theory of culture and pro-social behaviours [15,63]. In addition, previous studies mostly employed the TPB and NAM models to explain energy-saving behaviours, which overlooked the role of environmental and contextual factors on decision-making processes [7] and neglected the consequences of actual behaviours [14]. Therefore, this study used the SOBC framework to strengthen the integration of the TPB–NAM and to clearly explain the rational, moral, and contextual aspects of energy behaviours.

The findings of the current study make several significant contributions to both theoretical and empirical aspects. Regarding theoretical contributions, this study has five. Firstly, this study is the first to integrate the TPB and NAM models into the SOBC framework to explain energy-saving behaviours. Secondly, this study is the first to conceptualise the three antecedents of the TPB (subjective injunctive norms, subjective descriptive norms, and perceived behavioural control) and the two antecedents of the NAM (ascription of responsibility and awareness of consequences) as stimuli in the SOBC model. The findings confirm that these factors are effective stimuli which directly, positively, and significantly influence organisms (i.e., attitude and personal norms), and then indirectly drive behavioural responses (i.e., energy-saving intention and behaviour) and their consequences (i.e., energy-saving habits). Thirdly, besides examining the direct effect on the SOBC framework, this study also provides empirical evidence for the serial mediation mechanism of organisms and behavioural responses in the relationship between stimuli and consequences in an energy-saving context. Fourthly, the present study is the first to consider energy-saving habits as a consequence of energy-saving behaviours and examine this relationship. Finally, the moderation effects of cultural dimensions (i.e., collectivism and long-term orientation) on the energy-saving intention–behaviour relationship, as well as the relationship between energy-saving behaviours and habits, were first tested by this study.

Regarding the political aspect, the findings of this study provide some interventions to encourage residents’ energy-saving behaviours and energy-saving habits to achieve the Sustainable Development Goals. Firstly, the results of this study illustrate that both subjective injunctive and descriptive norms are important factors that not only shape a favourable attitude towards energy-saving but also indirectly encourage energy-saving intention, behaviours, and habits. Therefore, encouraging energy-saving practices by conveying information related to energy conservation among surrounding people can be an effective policy. This policy can be implemented through educational programs or mass media campaigns that are easily and freely accessible to everyone. Through these programmes, people can build a positive awareness of energy conservation and pro-social behaviours. Secondly, the results of this study also show that perceived behaviour control plays a crucial role in inspiring favourable energy-saving attitudes, intention, behaviours, and habits; therefore, policymakers should focus on ways to raise residents’ perceptions of the ease and convenience of energy-saving behaviours; for example, informing residents of some simple ways to save energy, such as turning off the lights or unplugging chargers when not in use. Thirdly, it is necessary to increase awareness of the consequences, personal responsibilities, and moral obligations regarding saving energy. Information about the environment and the global warming issue should be transmitted to everyone through conventional media channels, such as magazines, television, radio, and newspapers, along with the internet. Finally, policymakers should not neglect the informative role of cultural values in energy conservation practices since these values significantly increase the transformation from energy-saving intention into behaviours, and from behaviours into habits. Individuals should be encouraged to respect community values in their collective society and to contribute to the sustainable development of the community through educational programmes and communications in groups. The benefits to the community and society when implementing energy-saving behaviours could be transmitted via educational and communicative messages.

This study is not exempt from limitations. Firstly, even though this study is the first to test the moderate effect of cultural values on the relationships among energy-saving intentions, behaviours, and habits, data were only collected from residents in Vietnam. According to Chwialkowska and Bhatti [15], the nexus between sustainability and culture should be implemented in a cross-country context. Therefore, further studies should be implemented in different cultural contexts to clarify the role of cultural values in pro-social behaviours. Secondly, as a result of intercultural communication, culture is always changing over time, and therefore the influence of culture on individuals’ behaviours is also longitudinally shifted. Thus, further studies should employ a longitudinal method to expand our knowledge about the relationships among intention, behaviours, and habits, in addition to the effects of culture on sustainable settings, including energy-saving behaviours.