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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...

This paper presents an analysis of climate policy instruments for the decarbonisation of the global electricity sector in a non-equilibrium economic and technology diffusion perspective. Energy markets are driven by innovation, pathdependent technology choices and diffusion. However, conventional optimisation models lack detail on these aspects and have limited ability to address the effectiveness of policy interventions because they do not represent decision-making. As a result, known effects of technology lock-ins are liable to be underestimated. In contrast, our approach places investor decision-making at the core of the analysis and investigates how it drives the diffusion of low-carbon technology in a highly disaggregated, hybrid, global macroeconometric model, FTT:Power-E3MG. Ten scenarios to 2050 of the electricity sector in 21 regions exploring combinations of electricity policy instruments are analysed, including their climate impacts. We show that in a diffusion and path-dependent perspective, the impact of combinations of policies does not correspond to the sum of impacts of individual instruments: synergies exist between policy tools. We argue that the carbon price required to break the current fossil technology lock-in can be much lower when combined with other policies, and that a 90% decarbonisation of the electricity sector by 2050 is affordable without early scrapping.

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Whole-economy scenarios for limiting global warming to 1.5°C suggest that direct carbon emissions in the buildings sector should decrease to almost zero by 2050, but leave unanswered the question how this could be achieved by real-world policies. We simulate which policy measures could induce an almost complete decarbonisation of residential heating, the by far largest source of direct emissions in residential buildings. Under which assumptions is it possible, and how long would it take? We use the non-equilibrium bottom-up model FTT:Heat to simulate policies for a transition towards low-carbon heating in a context of inertia and bounded rationality, focusing on the uptake of heating systems. Our results indicate that the near-zero decarbonisation is achievable by 2050, but requires substantial policy efforts. We find that policy mixes are more effective for incentivising the uptake of fuelefficient low-carbon technologies, compared to a residential carbon tax as the only policy. In combination with subsidies and procurement policies for renewables, near-complete decarbonisation could be achieved with a tax of 50-200 €/tCO 2. Without being complimented by additional policies, carbon taxes show a decreasing marginal impact on total emission reductions, thus remaining insufficient for deep decarbonisation. In all scenarios, the decarbonisation of heating would increase projected heating costs faced by households initially, but could lead to cost reductions in most world regions in the medium term. We show that the potential impacts of policies highly depend on behavioural decisionmaking by households, especially in a context of deep decarbonisation and rapid transformation.