No abstract

Electrification of passenger road transport and household heating features prominently in current and planned policy frameworks to achieve greenhouse gas emissions reduction targets. However, since electricity generation involves using fossil fuels, it is not established where and when the replacement of fossil fuel-based technologies by electric cars and heat pumps can effectively reduce overall emissions. Could electrification policy backfire by promoting their diffusion before electricity is decarbonised? Here, we analyse current and future emissions trade-offs in 59 world regions with heterogeneous households, by combining forward-looking integrated assessment model simulations with bottom-up life-cycle assessment. We show that already under current carbon intensities of electricity generation, electric cars and heat pumps are less emission-intensive than fossil fuel-based alternatives in 53 world regions, representing 95% of global transport and heating demand. Even if future enduse electrification is not matched by rapid power sector decarbonisation, it likely avoids emissions in world regions representing 94% of global demand.Policy-makers widely consider electrification a key measure for decarbonizing road transport and household heating. Combined, they generate 24% of global fuel-combustion emissions and are the two major sources of direct carbon emissions by households [1][2][3][4][5] . For passenger road transport, plug-in battery electric vehicles ('EVs') are expected to gradually replace petrol and diesel vehicles ('petrol cars'). For heating, heat pumps ('HPs') are an alternative for gas, oil and coal heating systems ('fossil boilers'). Recent policy examples aimed at such end-use electrification include announced bans of petrol car sales, financial incentives for EV and HP purchases, planned phase-outs of gas heating, and the inclusion of HPs into the European Union's renewable heating targets 1,2,[6][7][8] . The use of EVs and HPs eliminates fossil fuel use and tailpipe/on-site greenhouse gas emissions ('emissions'), but causes emissions from electricity generation. Emission intensities in the power sector widely differ across the globe and will change over time 3 . Additionally, producing and recycling EVs and HPs involves higher emissions than producing petrol cars and fossil boilers, due to battery production for EVs, and refrigerant liquid use for HPs 9,10 . The question thus arises as to where and when the electrification of energy end-use could, under a failure to decarbonise electricity generation, increase overall emissions 11,12 .Multi-sectoral mitigation scenarios (such as those reviewed by the IPCC) have identified electrification as a robust policy strategy, but typically focus on a context of rapid power sector decarbonisation 3,13 . However, sector-specific policies and self-reinforcing social and industrial dynamics could as well lead to real-world trajectories in which end-use electrification and power sector decarbonisation take place at completely different rates 14 . In such a c...

The effectiveness of fiscal policy to influence vehicle purchases for emissions reductions in private passenger road transport depends on its ability to incentivise consumers to make choices oriented towards lower emissions vehicles. However, car purchase choices are known to be strongly socially determined, and this sector is highly diverse due to significant socio-economic differences between consumer groups. Here, we present a comprehensive dataset and analysis of the structure of the 2012 private passenger vehicle fleet-years in six major economies across the World (UK, USA, China, India, Japan and Brazil) in terms of price, engine size and emissions distributions. We argue that choices and aggregate elasticities of substitution can be predicted using this data, enabling us to evaluate the effectiveness of potential fiscal and technological change policies on fleet-year emissions reductions. We provide tools to do so based on the distributive structure of prices and emissions in segments of a diverse market, both for conventional as well as unconventional engine technologies. We find that markets differ significantly between nations, and that correlations between engine sizes, emissions and prices exist strongly in some markets and not strongly in others. We furthermore find that markets for unconventional engine technologies have patchy coverages of varying levels. These findings are interpreted in terms of policy strategy.