Scenarios limiting global warming to 1.5°C describe major transformations in energy supply and everrising energy demand. Here we provide a contrasting perspective by developing a narrative of future change based on observable trends that results in low energy demand. We describe and quantify changes in activity levels and energy intensity in the Global North and South for all major energy services. We project that global final energy demand by 2050 reduces to 245 EJ, around 40% lower than today despite rising population, income and activity. Using an integrated assessment modelling framework, we show how changes in the quantity and type of energy services drive structural change in intermediate and upstream supply sectors (energy and land use). Down-sizing the global energy system dramatically improves the feasibility of low-carbon supply-side transformation. Our scenario meets the 1.5°C climate target as well as many Sustainable Development Goals, without relying on negative emission technologies. * Contingency reserve of 8 EJ is allocated equally to Global North and South respectively. Bunker fuels are reported at the global level only, consistent with current energy balances and emission accounting frameworks. Activity level units vary per end-use service and upstream sector: a billion m 2 of floor space; b trillion passengerkilometres; c billion tonnes of materials; d trillion tonne-kilometres.

Meeting international climate targets requires accelerated low-carbon transformation. This means rapid technology diffusion which avoids carbon lock-in and has social legitimacy. More 'granular' energy technologies perform well on all three criteria. Granular technologies are small in size, low in cost, many in number, and distributed in application. Using a wide range of new data and analyses, we show that granularity is associated with faster diffusion, lower investment risk, faster learning, shorter lifetimes, lower complexity, larger efficiency potentials, more equitable access, more job creation, and higher returns on innovation investment. Although broadly robust to variations in context, these advantages are contingent on access to infrastructure, substitutability, and standardisation. Policy support for portfolios of granular energy technologies can help deliver rapid emission reductions in line with global climate change and sustainable development goals.

The demand for energy in buildings varies strongly across countries and climatic zones. These differences result from manifold factors, whose future evolution is uncertain. In order to assess buildings' energy demand across the 21 st century, we develop an energy demand model-EDGE-and apply it in an analytical scenario framework-the shared socioeconomic pathways (SSPs)-to take socioeconomic uncertainty into consideration. EDGE projects energy demand for five energy services, four fuel categories, and eleven regions covering the world. The analysis shows that, without further climate policies, global final energy demand from buildings could increase from 116 EJ/yr in 2010 to a range of 120-378 EJ/yr in 2100. Our results show a paradigm shift in buildings' energy demand: appliances, lighting and space cooling dominate demand, while the weight of space heating and cooking declines. The importance of developing countries increases and electricity becomes the main energy carrier. Our results are of high relevance for climate mitigation studies as they create detailed baselines that define the mitigation challenge: the stress on the energy supply system stemming from buildings will grow, though mainly in the form of electricity for which a number of options to decrease GHG emissions exist.