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.

Innovation processes during the early period of a technology's development establish the conditions for widespread commercialization. For comparative analysis of innovation processes across technologies, a common operational definition of the formative phase is needed. This paper develops a set of indicators to measure the start and end points of formative phases with reference to key innovation processes including experimentation and market formation. The indicators are then applied to measure the formative phase durations of sixteen energy technologies covering a range of historical periods and applications. Formative phases are found to last 22 years on average. Determinants of formative phase duration are explored. Duration does not appear to be explained by unit scale, up-scaling, nor initial cost. However, technologies that are ready substitutes for incumbents have shorter formative phases, ceteris paribus. Policy implications include the potentials and risks of accelerating formative phases to push low carbon technologies into the market.