Editing IPCC:AR6/WGIII/Chapter-6 (section)

==== 6.6.2.5 Using Less Energy and Using It More Efficiently ====

<div id="h3-28-siblings" class="h3-siblings"></div>

Demand-side or demand reduction strategies include technology efficiency improvements, strategies that reduce energy consumption or demand for energy services (such as reducing the use of personal transportation, often called ‘conservation’) ( [[#Creutzig--2018|Creutzig et al. 2018]] ), and strategies such as load curtailment.

Net-zero energy systems will use energy more efficiently than those of today ( ''high confidence'' ). Energy efficiency and energy use reduction strategies are generally identified as being flexible and cost-effective, with the potential for large-scale deployment (Chapters 5, 9, 10, and 11). For this reason, existing studies find that energy efficiency and demand reduction strategies will be important contributors to net-zero energy systems ( [[#Creutzig--2018|Creutzig et al. 2018]] ; [[#Davis--2018|Davis et al. 2018]] ; [[#DeAngelo--2021|DeAngelo et al. 2021]] ). Lower demand reduces the need for low-carbon energy or alternative fuel sources.

Characterising efficiency of net-zero energy systems is problematic due to measurement challenges ( ''high confidence'' ). Efficiency itself is difficult to define and measure across full economies ( [[#Saunders--2021|Saunders et al. 2021]] ). There is no single definition of energy efficiency and the definition understandably depends on the context used ( [[#Patterson--1996|Patterson 1996]] ), which ranges from device-level efficiency all the way to the efficient use of energy throughout an economy. Broadly, energy-efficient strategies allow for the same level of services or output while using less energy. At the level of the entire economy, measures such as primary or final energy per capita or per GDP are often used as a proxy for energy efficiency; these measures reflect not only efficiency, but also many other factors such as industrial structure, endowed natural resources, consumer preferences, policies, and regulations. Energy efficiency and other demand-side strategies represent such a large set of technologies, strategies, policies, market and consumers’ responses and policies that aggregate measures can be difficult to define ( [[#Saunders--2021|Saunders et al. 2021]] ).

Measurement issues notwithstanding, virtually all studies that address net-zero energy systems assume improved energy intensity in the future ( ''high confidence'' ). The overall efficiency outcomes and the access to such improvements across different nations, however, are not clear. Energy consumption will increase over time – despite energy efficiency improvements – due to population growth and development ( [[#DeAngelo--2021|DeAngelo et al. 2021]] ).

A study ( [[#DeAngelo--2021|DeAngelo et al. 2021]] ) reviewed 153 integrated asset management scenarios that attain net-zero energy sector CO 2 emissions and found that, under a scenario with net-zero emissions: global final energy per capita lies between 21–109 GJ per person (median: 57), in comparison to 2018 global final energy use of 55 GJ per person; many countries use far more energy per capita than today as their incomes increase; global final energy use per unit of economic output ranges from 0.7–2.2 EJ per trillion USD (median: 1.5), in comparison to 5 EJ per trillion USD in 2018; and the median final energy consumption is 529 EJ. By comparison, final energy consumption would be 550 EJ if current energy consumption per capita continued under a future population of 10 billion people. Across all scenarios, total final energy consumption is higher today than in the year in which net-zero emissions are attained, and regionally, only the OECD+EU and Eurasia have lower median total final energy than in 2010.

Net-zero energy systems will be characterised by greater efficiency and more efficient use of energy across all sectors ( ''high confidence'' ). Road transportation efficiency improvements will require a shift from liquid fuels (Chapters 5 and 10). Emissions reductions will come from a transition to electricity, hydrogen, or synthetic fuels produced with low-carbon energy sources or processes. Vehicle automation, ride-hailing services, online shopping with door delivery services, and new solutions like last mile delivery with drones may result in increased service share. Lighter vehicles, a shift to public transit, and incorporation of two- and three-wheelers will be features of a net-zero energy system (Chapter 10). Teleworking and automation of work may provide reductions in driving needs. Other sectors, such as air travel and marine transportation may rely on alternative fuels such as biofuels, synthetic fuels, ammonia, produced with zero carbon energy source ( [[#6.6.2.4|Section 6.6.2.4]] ).

Under net-zero energy systems, buildings would by characterised by improved construction materials, an increase in multi-family dwellings, early retirement of inefficient buildings, smaller floor areas, and smart controls to optimise energy use in the building, namely for heating, cooling, LED lighting, and water heating (Chapter 9). End uses would utilise electricity, or potentially hydrogen, produced from zero-carbon sources. The use of electricity for heating and cooking may often be a less efficient process at converting primary energy to energy services than using natural gas, but using natural gas would require CDR in order to be considered net-zero emissions. Changes in behaviour may modestly lower demand. Most economies would have buildings with more efficient technologies powered by zero-carbon electricity, and developing economics would shift from biomass to electricity, raising their energy consumption as population and wealth increase under net-zero energy systems.

Industry has seen major efficiency improvements in the past, but many processes are now close to their thermodynamic limits. Electrification and breakthrough processes (such as producing steel with electricity and hydrogen), using recycled materials, using heat more efficiently by improving thermal insulation, and using waste heat for heat pumps, as well using advanced sensors, monitoring, and visualisation and communication technologies may provide further efficiency improvements (Chapter 11).

<div id="6.6.2.6" class="h3-container"></div>

<span id="greater-reliance-on-integrated-energy-system-approaches"></span>