Of actors, cities and energy systems: advancing the transformative potential of urban electrification

Electrification of transportation and buildings connected to clean grids has been touted as one of the key solutions to the global decarbonization challenge [1]. Cities are at the frontline of current and future electrification, as they concentrate populations, economic activities and infrastructures that depend on and drive electricity generation, distribution, and use. City actors occupy a central role in the electrification actions that enable and support energy transitions in efficient, equitable, environmentally sound and resilient ways [2, 3]. With 4.1 billion people living in urban areas, globally, cities generate about 80% of gross domestic product (GDP), consume about 75% of global primary energy, and are the source of over 70% of energy-related carbon dioxide (CO₂) emission [4, 5]. Yet, even in cities, particularly those in developing countries, 97 million lack electricity [6]. Cities are vulnerable to power disruptions, as numerous recent cases, such as heatwaves, wildfires, and hurricanes have demonstrated. Further electrification will alter those vulnerabilities in complex ways. Cities are also fundamental in advancing the United Nations' sustainable development goals (SDG), including those for affordable, reliable, and sustainable energy services (Goal #7); climate action (Goal #13); and inclusive urban resilience (Goal #11) [7].

Although the decarbonization impacts of electrification are well documented at the national level, scholarship on the relevance of urban electrification to the sustainability of the current energy transition is lacking [8]. Research is occurring in discrete fields (e.g. urban research vs. governance research and transportation or building research vs. grid modeling). Furthermore, research is dominated by analyses seeking to inform optimal technological and economic solutions to the decarbonization potential of electrifying end-uses, [9–11] including infrastructure; [9, 12–20] or grid and end-use interconnections [21–25]. It is also dominated by examination of the future of electricity demand and supply under different electrification scenarios [1, 26, 27].

This topical review seeks to widen the field-of-view on urban electrification [28–33] by reviewing existing knowledge on (a) the multiscale drivers and actions underway to achieve widespread electrification of transportation and integrate electric vehicles (EVs) with buildings connected to clean grids in cities; and (b) the social, economic, technological, environmental and governance conditions defining barriers and options, path dependencies, and levers of change [34]. Central to this review is to elucidate critical questions regarding (a) the navigation of complex urban systems processes; (b) the endpoints towards which urban electrification is directed; and (c) the drivers and implications of actions.

Urban electrification refers, first, to the process of providing populations, particularly more than one billion people currently lacking it, with modern types of electricity. Second, urban electrification refers to the increased use of electricity as an alternative fuel for transportation and buildings, and the coupling of built environment designs with the development of electricity provision systems [27]. For cities that have not previously been fully electrified, this process includes the possibility to 'leapfrog', skip altogether, fossil fuel-based generation and directly adopt sustainably powered electricity sources [35].

This topical review focuses on actions seeking to electrify transportation and integrate EVs with buildings connected to clean grids, as electric cars, motorbikes, buses and light-duty trucks need to be charged in residential, commercial and governmental buildings. This has instigated, in recent years, analysis and strategies seeking to manage the time and speed of charging in buildings, of building design and/or retrofitting, and of EV-charging interactions with adaptive, flexible, clean and redundant grids []. In many cities, EVs are being integrated with buildings, charging infrastructure and photovoltaic panels (PVs) in many promising ways. For instance, through EV to grid and renewable energy integration [21, 22, 30, 36]; through the integrated management of buildings and distributed energy resources (DERs) [21, 23, 37]; and through land use approaches to planning of EV charging infrastructure [38–40].

Urban electrification is a multiscale process. It involves not only the distribution and use of electricity within a city boundary, but also its provision by grids and distribution networks that reach into rural areas (figure 1) [41]. This means that although we will focus on key connections among transportation, buildings and the grid, when needed we will point to effects outside of the demarcations of city limits, such as power plants in rural areas [42]. We will also point to how these uses are affected by actions and processes beyond city boundaries, such as regulations, or climate change. Urban electrification is, therefore, a multi-scale process requiring action across a range of actors across sectors and jurisdictions. Interestingly, the scales at which urban electricity systems operate often do not fit with the scales at which they are understood and managed, and this 'lack of fit' may create undesirable outcomes [43]. For instance, large-scale hydro-power, solar or wind generation, while managed to provide electricity to an urbanizing region, often creates problems of fit with and externalities to outside regions and communities depending on these resources [44].

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In the next sections, we will examine existing knowledge on the drivers of urban electrification in these sectors at three levels, which lie both inside and outside the city [28, 30, 31, 45, 46]:

• The incumbent system organizing urban uses of electricity, and structuring relationships amongst EV manufacturers, regulators, and grid operators whose priorities and understanding of appropriate ways to integrate EVs with buildings connected to a clean grid are intertwined with the expectations and practices of users (e.g. range anxiety, lifestyles, or cultural identity). These are the incumbents, the legacy industrial and regulatory schemes under which we currently operate (section 3.1).
• A broader level of economic and social trends, climatic processes, and normative values and visions (e.g. of prosperity, or sustainability) that structurally shape actions. (section 3.2).
• The niche level, where market, technology, and societal actions fostering electrification emerge, evolve, and compete for resources and for realignments [47] different actions (to be described in section 3.3).

3.1. Current urban electric systems

Centralized power systems have dominated the unprecedented growth, in the 20th century, of mass production, delivery and consumption of electricity, stretched across city-regions through a nation-wide (and sometimes multi-national) grid, and aimed helping create the 24/7/365 requirements of urban residential, commercial and industrial consumers [48].

Global electricity consumption has risen by about 70% since 2000. The rate of growth in electricity supply and consumption, the largest single source of GHG emissions in most countries, is greater than that for energy overall (figure 2). The steady increase in electricity demand means that the current electrification shift is turning electricity into the second largest energy source by end-use (the first is oil) [26]. Light and heavy industry is the number one source of electricity demand in developing economies, whereas in advanced economies, the buildings sector is the largest user. Transport's share is the lowest but is projected, globally, to experience the fastest growth in electrification levels [26, 27]. These shifts explain the current focus on transport electrification through integration of EVs with buildings connected to a clean grid.

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Estimations of urban consumption of electricity are severely limited by the lack of data [50, 51]. Still, scholarship agrees that electrification varies across countries and from urban to rural areas differently, affecting energy supply and social practices of energy use differently (Figure 3) [6]. For instance, while in the United States and Europe, access to electricity is nearly universal, urban to rural differences in access exist in lower-income countries, particularly in Sub-Saharan Africa [49]. The statistical association in figure 3 shows that electrification and urbanization are deeply related with each other and with wealth (GDP). At every level of electrification, however, there is high variability in GDP per capita, with higher income countries tending to deliver much higher socio-economic impact from energy services across rural to urban gradients than others do [52].

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The central curve also highlights that lack of good quality electricity has negative impacts on the productivity and quality of life of extremely poor places inhabited by 1.1 billion people, particularly in urban slums, accounting for between 10% and 65% of the urban population in the global South [53]. The challenge here is to know which settlements and populations are more suitable for innovative urban electrification, and what the potential for leapfrogging is. For instance, of skipping existing electricity systems, electrifying motorbikes, three-wheelers, buses, cars, new buildings or retrofitting existing buildings and connecting these users to electricity fueled by renewables, with shared assets or distributed ownership, and of doing this through integrated energy planning [35].

3.2. Broader drivers

3.3. Niche actions with the potential to shift urban electricity systems

By and large, actions to electrify transportation and integrate EVs with grid-connected buildings fueled by renewables are creating change and have the potential to drive significantly more. However, these are niche-level actions for two reasons. First, their promoters are competing with the actors and elements of current urban electric systems. To realize the transformational potential of these actions, dramatic changes are needed in society, technology, governance, markets, and users' practices [30]. This can be seen in the still low levels of penetration of EVs, in cities and of communities of buildings connected to grids fueled by renewables. In 2017 only 25 cities were home to almost 1.4 million of the world's 3.1 million EVs. Eleven are located in China (Beijing, Changsha, Chongqing, Guangzhou, Hangzhou, Qingdao, Shanghai, Shenzhen, Tianjin, Wuhan, and Zhengzhou); six in the United States (Los Angeles, New York, San Diego, San Francisco, San Jose, and Seattle); six in Europe (London, England; Paris, France; Amsterdam, Netherlands; Bergen and Oslo, Norway; and Stockholm, Sweden); and two in Japan (Tokyo and Kyoto) [108].

Second, while these actions can be adopted at the individual level among generally wealthier populations and on an experimental basis by specific communities, their larger-scale and inclusive growth requires changes in urban infrastructural and institutional organization, which are path dependent. As such they impose a logic and direction for incremental sociotechnical change along established pathways of design, deployment, and use [106]. For instance, the low-density urban form of many North American cities has been largely the result of freeway construction programs and land use regulations [42, 107, 108]. Infrastructural and behavioral path dependencies resulting from these actions have created low-density patterns of settlement and a dependence on private vehicles, associated with more electricity use [109–111], and now focusing a high level of attention and public electrification investment on personal vehicles.

Furthermore, historically cities have been the main organizational level for centralized regimes operated by electricity grids and utilities [30, 112]. These regimes remain important today even as the governance of electricity systems has diversified with regional utility consolidation and market development [109], and with the emergence of a suite of social and commercial organizational models, from those owned by consumers, communities, and cooperatives to those leased to energy companies [48]. Therefore, existing patterns of infrastructure and governance have profound influences on the design and scaling of electrification and integration of EVs with buildings connected to clean grids, and can produce inequitable outcomes. There are numerous examples of green electrification policies that are inaccessible to the most disadvantaged communities. In the U.S., for example, federal tax credits for EVs, home battery systems, and PVs are not 'inclusive' policies because they are largely unavailable to low-income households due to affordability barriers and limited tax liability [113].

Not only are options to foster urban electrification associated with benefits and barriers, but actions are also likely to create new forms of risks and vulnerabilities (e.g. privacy risks associated with the rise of smart energy systems) that are not only technological or economic but also social, institutional, economic and environmental. Here, we summarize what is known about social, economic, technological environmental and governance (SETEG) options, benefits, and barriers, which often do not exist in clearly defined classes (table 1) [30, 114]. For instance, economic benefits may synergize with health and environmental benefits, but may require tradeoffs with social equity.

Efforts to electrify transportation and integrate EVs with buildings connected to clean grids are often associated with economic, societal, and environmental benefits such as improvements in people's quality of life and health, protection of ecosystems, and safeguarding of ecosystem services for future generations [9]. Climate and atmospheric benefits can accrue via the electrification of transport and buildings, with additional benefits for fuel costs and human health [115, 116]. However, these benefits are variable depending on factors such as the generation mix of the electricity grid [23]. Moreover, because electrification has been historically designed and built (especially in developed countries) with fewer electrified end-uses in mind, users' needs for affordable and accessible devices are often neglected [117]. New electrification trends, which are opening up co-optimization opportunities, might also disrupt electricity systems and could cause integration issues, especially at the distribution level, that should be planned for and addressed [97–99].

The equity impacts of electrification are also variable, depending on the policies used to promote the transition. The nature and location of energy financing and infrastructure investments can cause low-income households to benefit or lose. For example, few low-income households participate in EV, charging, storage and solar programs, but these programs are financed by raising the electric rates of all customers [118, 119–121]. While such inequitable impacts of electricity tariffs can be offset by modest low-income energy assistance programs (e.g. the federal LIHEAP program in the United States) or subsidized EV access, such as the BlueLA EV carshare in low-income Los Angeles communities, such support is widely variable depending on city, state, municipality, country, and utility provider [118, 119–121]. Another challenge is the general formulation of energy innovation policies through markets and incentivization, both of which create obstacles against adoption of new technologies by low-income populations. Poor individuals and families often lack up-front resources to take advantage of long-term savings from more efficient or alternative energy technologies, are less likely to own their residences, and have lower credit scores. Therefore, new policy approaches are required to transform electrification innovation into a strategy for poverty alleviation [122].

User perceptions and culture—as manifested in lack of familiarity with emerging technologies (e.g. EVs and PVs), cultural and status expectations of comfort, anxiety and distrust, or just lack of knowledge—can become crucial sources of social barriers [123–125]. For instance, sociological studies on the use of air conditioning have shown that rather than only temperature or human physiology, gender, status, and sociocultural conventions shape comfort [123]. Even as the cost of EVs becomes a less relevant concern, customers still experience worry about depleting their battery's charge before reaching their destination, or waiting for their EVs to charge. In residential buildings, natural gas cook tops and fireplaces may be challenging to electrify due to consumer cultural preferences [126]. Understanding societal barriers is challenging as they vary across location, gender, education, income, and cultural and political preferences.

As for the economic dimension, while the cost of new technologies often decreases over time, and varies depending on location, the accessibility to, particularly in developing-country cities, and affordability of items such as electricity services, EVs, and PVs, or the availability of funding to foster their use can become barriers [125]. For example, in a study of EV and vehicle-to-grid (V2G) technologies in Nordic countries, known for their leadership in this field globally, Noel et al [30] found that economic barriers result not only from lack of production in EV and V2G technologies, but also from still higher marginal costs as compared with those of ICEs, even if operating costs are lower. This is indicative of the economic and social complexities consumers face when making choices related to new, and at times 'unproven' technologies.

Substantial technical challenges related to the provision of electricity through renewables include the need to grow low-carbon energy storage capabilities, to develop new demand management capabilities, and to create distribution infrastructure able to deal with variations in power demand loads associated with changes in EVs, buildings and behavior. Each of these developments can help mitigate mismatches in the spatial and temporal patterns of supply and demand of zero-carbon energy generation. These mismatches, which have beset the electrical industry since its very beginning, have historically been addressed using stored energy in the form of hydrocarbon fuels, regional transmission infrastructures, pumped hydro, and extensive demand management approaches, from investment in industries in all these fields to demand charges and the right to turn off large customers during peak demand periods. Future strategies are likely to depend on multiple technologies, including distributed energy generation and storage, flexible low-carbon fuels (such as hydrogen or utilization of captured carbon), renewables, grid-scale storage, internet of things-enabled advanced demand management, and new transmission corridors [127].

The urban form or morphology of cities can pose barriers such as inadequate charging infrastructure and PV installation, historical zoning codes that prohibit PV, or inappropriate charging space [38, 128]. Charging, storage and PVs face extremely high competition for urban space, which constrain their potential to become a primary feature of building surfaces. For instance, the building stock of a city determines how much electricity can be generated from PV panels, which benefits from being angled in a direction that maximizes sun exposure; the building stock also constrains the amount of space available for EV charging in buildings, parking areas and other spaces. Furthermore, the current organization of the electrical industry could be disrupted if charging infrastructure and PVs significantly impact ownership, demand, or management of energy distribution and if technological improvements continue to contribute to improvements in panel efficiency and integration with buildings and EVs [129].

Governance arrangements also pose barriers to urban electrification [130]. In countries worldwide such as Spain, Austria, the United States, South Korea, the United Kingdom, Mexico, and the Netherlands, policy supports for EVs, charging, and electrified building devices, such as regulations, incentives, investments, and taxations can be removed, weakened, or just inadequate [74]. At the same time, local and state governments are acting independently in pursuit of mitigation actions, often in spite of the lack of comprehensive or ambitious policy at the national level [131–133]. Despite their ambitions, these actors are constrained in their capacity to influence national policy [134] and face barriers related to influence, resources, and political culture [135]. Often barriers arise out of the lack of vertical integration in decision making, including the multiplicity of shifting or competing priorities with which city officials dealing with transportation and buildings grapple [74]. In larger urban areas, such as New York City, Mexico City, and Dakar, which may have governments comprised of two or more local and even state authorities, each authority can act only within its jurisdictional remit (e.g. transport, building design). In this diffusion of power, the overall impact of one authority may be limited unless there is horizontal collaboration among sectors and local authorities, or an overarching strategic metropolitan authority exists to ensure regional action [74]. The lack of fit between sectoral and jurisdictional levels at which transportation, buildings and the grid function and the scales at which they are understood and managed is another, underexplored, source of governance barriers [42].

City officials, particularly in lower-income countries, often face financial, human resource, and institutional barriers. For instance, a study in Mexico City found that initial costs of adopting electric buses, minibuses and cars are too high both for providers and users of transportation services. To avoid unplanned growth of electromobility, they suggested to first reorder uses of urban space by different transport modes. Considering the diversity of mobility segments (from micro-mobility to public transport freight), they also suggested to identify priorities, and generate route maps that fit each of these segments and help guide policy design and implementation mechanisms [136]. In many cities of low-income countries, actions often depend on foreign financial aid. It has been found that international sponsors frequently lack the financial, human, and institutional capabilities to identify and adapt expensive technologies to local needs, for instance for affordable and easy-to-maintain technological options [125].

This section takes stock of the review of existing knowledge and looks towards the creation of a more integrated research agenda. It reflects on how accelerated rates of societal, political, environmental, and technological change are opening options to help realize the transformational potential of a crucial elements of urban electrification: integrating electrified vehicles with buildings connected to clean grids.

Notwithstanding the myriad actions underway, we do not know which combinations of actions can most efficiently achieve crucial societal outcomes advancing the SDGs, such as enhanced decarbonization, equity, human health and resilience. We also do not know where, for whom, and when, and why they are most effective [114]. Nor do we know how diverse pathways of urban electrification measure against, or can be leveraged to advance these outcome criteria. Robust tools and methods are also needed to analyze costs, risks, co-benefits, and trade-offs.

Methodologies are needed that explicitly include actions, together with infrastructures, technologies, markets, climate, and governance. This is fundamental to analyzing and simulating how the coming together of SETEG factors shape barriers and enablers and generates pressures for and against energy transitions.

To overcome an existing focus on one element at a time, integrated and innovative capabilities are needed that incorporate emergent system interactions not only among EVs, buildings and clean grids, or across scales but also among SETEG factors that might not be handled by purely techno-economic models. Identified elements requiring research include:

• (a)  
  Links between sectoral elements of urban electricity systems—for example among transportation, buildings and the grid.
• (b)  
  Links between local and transboundary elements of urban electricity systems—for example between local use and extra local impacts of battery production and disposal that can only be captured with life-cycle analyses [137].
• (c)  
  Mechanisms by which interdependent infrastructure and actions affect electricity supply and use, and their resilience to extremes, pandemics, cyberattacks, and other disruptions.
• (d)  
  Business models required to co-optimize multiple systems and send proper signals (e.g. electricity pricing) to multiple actors.

While the common themes of importance like flexibility, reliability, and affordability of EVs, charging and building construction or retrofit are shared across urban geographies, what options to achieve electrified mobility, or buildings connected to clean grids look like on the ground vary with scale, and often remain context specific. For example, differences between charging infrastructure and sizes of EVs are shaped by a combination of built environment and social forces (like ability to afford or building design). Electrification in poor, vulnerable, or slum urban areas remains a challenge, as they lack adequate electricity services. Thus, they require particular care in the design and application of tools that help to 'leapfrog', skip altogether, electrification of buildings and transport fueled with coal or combustibles and directly adopt sustainably powered electricity sources [128, 138, 139]. Therefore, the following studies are needed to complement modeling efforts:

• (a)  
  Comparative studies, for instance, of options and barriers to integrating EVs, charging and building construction or retrofit in growing urban areas vs existing urban areas; dense urban cores vs. sprawling suburban and exurban landscapes; and mega-cities vs. small and medium-sized cities.
• (b)  
  Typologies to examine variations within and across cities in SETEG factors shaping options and barriers [140].
• (c)  
  Case study approaches that inform and are informed by (a) to (b) by digging deep into understanding SETEG barriers and opportunities on the ground.

There is a need to develop coordinated research, testing, demonstration and deployment on advanced transport electrification integrated with building and grid systems. State of the art analytics, tools and data are needed to:

• (a)  
  Create power distribution systems that handle variations in power demand loads associated with changes in EVs use and charging behavior in commercial, public and residential buildings.
• (b)  
  Understand the sociodemographic, economic and cultural factors determining differences in behavioral practices that can inform power system, electro-mobility planning and building configuration.
• (c)  
  Inform optimization of investments in charging infrastructure integrated with distributed energy systems in buildings and communities.
• (d)  
  Use of state-of-the-art adaptive controls (for charging in buildings and power distribution) that respond to variable interconnected resources.

A sound understanding is needed of how values, visions, and expectations—for example, of smart cities—broadly shape actors' motivations, preferences for, and actions in steering urban electrification. Action items for research in this topic include:

• (a)  
  Localized scenarios for the emerging urban electrification that incorporate actors' visions and help them identify local actions to enhance goals such as equitable, advanced transport electrification integrated with building and decarbonized grid systems.
• (b)  
  Social impact assessments to improve understanding of how the shifting energy landscape of SETEG factors relates with cost, access, and affordability.
• (c)  
  City resilience planning and financing, particularly under scenarios of pervasive electrification, where the nature of redundancies and energy storage will be substantially different.

Rapid economic and technological change is creating transformational opportunities for advanced transport electrification integrated with building and decarbonized grid systems, a promising component of urban electrification. Yet there remains an open question as to whether this integration can be developed in ways that support sustainable, resilient, and equitable energy transitions. The suggested approach to analyze SETEG factors shaping options and barriers, offers an important instrument to help identify tradeoffs and harness synergies and opportunities for the public benefit. For instance, by developing tools, models and data to accurately account for the impact of EV charging on building energy use, on-site renewable energy generation and storage—and coupling these factors with consumer constraints and preferences and governance issues—better options can be identified to develop power distribution systems that effectively handle spatial and temporal variations in power demand loads. In moving forward, we must also explore and acknowledge current and future systemic risks, while embracing the positive elements of change such as more choices, greater affordability, and accessibility, while also meeting consumer needs.

In this effort, divergent communities of scholars (working on transportation, buildings, behavior and urban planning) need to come together and adapt their scoped analytical and policy frameworks of urban electrification to incorporate other views of the process, and, through integration, create a broader perspective. This perspective must take into account learning and experimentation but also understand the limits or gains imposed by coalitions of interests that can block or support emerging niche-innovations. To leave the empirically rich and socially complex topic of urban electrification to modelers and rational actor theories alone is to create a picture with dots and lines to represent people and places and things. However, since people rarely behave like dots and lines, such pictures, no matter how ingenious, can never carry us quite to where we want to arrive.

No new data were created or analyzed in this study.