Sustainable Cities: How are they measured and what can we learn?

April 19, 2026

By Brooke Cupelli

Sustainability is a growing global priority. With individual efforts, businesses making genuine green growth, and continued progress in policy, sustainability is proving to be a global mutual goal. There are many leaders in sustainable practices globally, across countless sectors. One way we can investigate practices that are working and identify growth opportunities is by examining the most sustainable cities in the world. With worldwide urban growth, leading to increased resource consumption and an active climate change crisis, cities pose many problems, but they answer with hopeful innovations.

Looking at a city as a complete ecosystem, or organism, “with every individual action affecting the entire body” or city, allows for a greater chance of positive change (Downes, 2024). Regular efforts are being made to go green, with city infrastructure being continually integrated into individual goals and policy changes. Although there is a clear desire for a more sustainable future, there are great strides left to be made. Learning from the examples of current successes across the globe allows further progress.

Currently, “55 percent of the world’s population lives in urban areas” (i.e., cities) with a projected 13 percent growth resulting in a 69 percent increase by 2050 (United Nations, 2018). As over half of the global population lives in “urban environments, moving towards sustainable cities is vital to our health as well as the future of the planet” (21 Most Eco-Friendly Cities, 2024).

What is a sustainable city?

A sustainable city (also known as a green city) is a city that collectively works to foster the health, well-being, and growth of the inhabitants and the natural environment (Best Green Cities, 2025). Ultimately, the sustainable city meets the needs of present citizens “without compromising the ability of future generations to meet their own needs, reconciling the environment, social and economic ‘pillars’ of long-term durability” (Laconte, 2018). Sustainable cities all contain various characteristics. Typically, cities known for being green have policies regarding renewable energy, construction/ expansion and the reduction of carbon emissions (Biro, 2025). As previously mentioned, sustainability requires an all-inclusive approach. Sustainability applies to individual buildings and neighbourhoods, then broadens to the city as a whole (including its peripheries and regional boundaries) (Laconte, 2018).

Measuring the sustainability practices of a city

There are no defined global parameters used to measure a city’s sustainability practices. Although this does cause challenges in comparative studies, it does allow for the consideration of regional diversity, evolving science, and further variables. Many studies aim to systematically compare sustainability practices at multiple geographic levels in order to formulate study-specific benchmarks. Many studies have assessment criteria that reflect political orientation, as current and active policy aims to enact change (Laconte, 2018). The assessment of government policies, paired with community practices and current infrastructure, all determine whether a city is deemed ‘green’ (Best Green Cities, 2025). This further reinforces the need for a holistic interdisciplinary approach when creating and determining what makes a city sustainable.

The ‘greenness’ of a city exists on a multifaceted spectrum (Best Green Cities, 2025). In the current time, there is no standardized ranking system to determine the most sustainable city in the world. There are many lists, with overlapping data, revealing commonly high-ranking cities. The list(s) cannot be static but are formed and revised (21 Most Eco-Friendly Cities, 2024).

Countries in their entirety are commonly measured on the Environmental Performance Index (EPI) (21 Most Eco-Friendly Cities, 2024). Formulated through Yale University, the EPI “provides a data-driven summary of the state of sustainability around the world” (Block et al., 2024). Updated annually, the EPI uses “58 performance indicators across 11 issue categories” (Block et al., 2024). With 180 countries being ranked for their climate change performance, environmental health, and ecosystem vitality,” it has proven to be a valid barometer in data collection (Block et al., 2024). Although not used in a widespread manner, at “a local and municipal level, the most eco-friendly cities [can be] ranked according to a similar system, known as the Siemens Green City Index” (21 Most Eco-Friendly Cities, 2024). Although this index is not globally standardized, it holds many common factors with the collected input of the studies I have examined and is a concise, research-based model that can be easily followed.

Siemens Green City Index

The Siemens Green City Index (GCI) uses a complex formula that considers a number of factors (21 Most Eco-Friendly Cities, 2024). The European GCI evaluates 16 quantitative indicators and 14 qualitative indicators (Economist, 2012). With the core factors developed for assessing European cities starting in 2009, the methodology for Europe was then adapted to create other regional indices (Economist, 2012). The expansion and alteration of the index are important to properly reflect accurate data sets per city. The GCI has measured over 120 cities since its inception.

Structure of the Siemens Green City Index (Source: Siemens 2012: 9)

The initial GCI European Index identified 8 key categories of: CO2, energy, buildings, transport, waste & land use, water, air quality, and environmental governance (Economist, 2012). For example, in the most current US and Canada Green City Index study, the only difference from the categories identified above was the differentiation of waste and land use into their respective sections, rather than in combination (Economist, 2012 & Economist, 2011). Within the 8 key categories, there are further points of evaluation (as stated above), resulting in 30 different indicators.

They are as follows:

CO2

CO2 intensity
CO2 emissions
CO2 reduction strategy

Energy

Energy consumption
Energy intensity
Renewable energy consumption
Clean and efficient energy policies

Buildings

Energy consumption of residential buildings
Energy-efficient buildings standards
Energy-efficient buildings initiatives

Transport

Use of non-car transport
Size of non-car transport network
Green transport promotion
Congestion reduction policies

Waste & land use

Municipal waste production
Waste recycling
Waste reduction policies
Green land use policies

Water

Water consumption
System leakages
Wastewater systems treatment
Water efficiency and treatment policies

Air quality

Nitrogen dioxide
Sulphur dioxide
Ozone
Particulate matter
Clean air policies

Environmental Governance

Green action plan
Green management
Public participation in green policy (Economist, 2012).

Through the process of cross-referencing data from studies and lists made in 2024, many countries had multiple cities on lists, while some had single mentions, if any. Many of the studies differ in scoring measures. In one study, the GCI was the initial reference, in combination with more recent (unnamed) initiatives (21 Most Eco-Friendly Cities, 2024). All of these lists had some semblance of a scoring system very similar to that of the GCI.

This list compiles some of the most environmentally conscious cities, exclusively including cities on three or more lists (from a pool of six published 2024 studies), as well as mentioned on the GCI, to establish a definitive reference point for measurement.

The most sustainable cities in the world (some of them, and in no particular order):

Vancouver, Canada

Vancouver is one of the “first major North American cities to develop a 100 percent renewable energy target for its electricity supply” (Downes, 2024). With 95 percent of this goal reached as of 2023, policy is becoming reality in Vancouver. The city is designed and “driven by eco-density, [meaning] more vertical development and less urban sprawl” (Downes, 2024). With an emphasis on local produce consumption, green jobs, and alternative transportation (bikes and public transport), Vancouver is one of the most sustainable cities in Canada (21 Most Eco-Friendly Cities, 2024).

London, United Kingdom

Much of the sustainable progress in London is driven and “coordinated by the London Sustainable Development Commission (LSDC)” founded in 2002 (Downes, 2024). In 2019 London became the world’s first National Park City, “a city where people, places, and nature are better connected” (Shilling, 2025). With simple and complex initiatives, the city has employed many sustainability practices. For example, access to free drinking water fountains across the city dispensed an equivalent amount of water to 1.4 million single-use plastic bottles (Downes, 2024 & London City Hall, 2024) London has lofty sustainability goals, such as “being zero-carbon by 2050” (Biro, 2025).

Lahti, Finland

Lahti was named the European Green Capital in 2021 (Downes, 2024). Two years previous to that, they set out to become carbon-neutral by 2025 (Facts, 2024). With positive progress made on this goal but no official update, it is forecasted “that carbon neutrality could be achievable by 2028” (Lahti, 2024). Lahti is experimental and innovative when encouraging public participation in piloting sustainable programs. They are the first country in the world to pilot an app for personal carbon-trading for residents, incentivizing the use of alternative green transportation, particularly cycling (CitiCAP, 2020).

Copenhagen, Denmark

Copenhagen’s large-scale sustainability successes come from its “bike-centric and pedestrian-friendly infrastructure,” vigorous recycling programs, and green electricity initiatives (Biro, 2025, 21 Most Eco-Friendly Cities, 2024). 230 miles of bike lanes within city limits have allowed the city to remove one-third of all fossil-fuel-reliant transportation (Biro, 2025). Further, Copenhagen has been able to eliminate approximately 90,000 metric tons of greenhouse gas emissions each year since 2019 (Biro, 2025). The city has a goal of carbon neutrality set for this year (no data regarding the success or delay of this target is currently published). Although this goal may not be met this year, Copenhagen has “reduced its emissions by 75 percent since 2005” (Garric & Strek, 2024). It is currently rated the most eco-friendly European city (21 Most Eco-Friendly Cities, 2024).

Oslo, Norway

Named the European Green Capital in 2019, two years before Lahti (Downes, 2024). “It was the first city in the world to have a climate budget” and aims for climate-neutrality by 2030 (Downes, 2024). Oslo is revered for its emphasis on sustainable transport, with 82 percent of new car sales being electric in 2023 (Best Green Cities, 2025). The city has a mandate which requires all new municipality-built buildings to be energy-plus (not only zero-emission but also sources of energy generation) (21 Most Eco-Friendly Cities, 2024). “Emissions are being tracked citywide” and municipal pension funds are investing in green projects (21 Most Eco-Friendly Cities, 2024).

Stockholm, Sweden

Stockholm has decreased its climate impact and greenhouse gas emissions by more than half since 1990, even with substantial population growth (Downes, 2024). Stockholm takes a holistic approach to sustainability with 60 percent of electricity coming from renewable sources, a vast network of food banks committed to diverting waste, and energy-efficient building standards (Downes, 2024 & 21 Most Eco-Friendly Cities, 2024) The city “emphasizes the human rights aspect of environmental challenges,” which encourages a high amount of participation and engagement from its citizens in recycling programs and beyond (Best Green Cities, 2025). Stockholm has many protected green spaces, with an estimated 80 percent of the city’s population living within a 5-minute walk from a park or green space (21 Most Eco-Friendly Cities, 2024). Of all major cities in Europe, Stockholm has the best air quality 21 Most Eco-Friendly Cities, 2024).

Key takeaways

Please note that cities like San Francisco (USA), Sydney (AUS) and Singapore (SGP) each appeared on two lists. The cities with multiple mentions ranged in population from just over 121 thousand people (Lahti) to just under 9 million people (London), with the average city on the list ranging from 1 to 2 million people (London’s Population Projections, 2022 & Europe, 2024). As previously stated, through the lack of standardized global testing parameters, no list regarding sustainable cities can remain static or completely precise. Noting where overlap occurs allows for a better understanding of measurable criteria for successful sustainable city models.

It is clear through the substantial presence of European cities on this list, that European cities outrank much of the world in their ability to enact sustainability practices into their city structures. Their success ultimately comes from an integrated approach with efficient use and application of governance. Alongside policy, there must be opportunities for bringing nature into cities, investing in urban societal resilience, and incentivizing citizen participation (Jones, 2025 & Urban Sustainability, 2024). Culture is a key component in the “liveability and sustainability of growing metropolitan cities” (Moonen, 2019).

Current projections state that two-thirds of the global population will live in cities by 2050 (United Nations, 2018). The urban world needs practical and constant sustainable adjustments with realistic target goals. A vision of the future must align with the development of sustainable cities, focusing on a combination of economic, social, and environmental development (Biro, 2025). Many positive changes are happening globally; this is not enough. Effective action must be consistently taken across areas of opportunity, one being furthering sustainable cities (Urban Sustainability, 2024). Achieving greener cities is a crucial step in the global management of climate change.

References

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