Electrofuels from CO2 and H2O have recently emerged as a promising alternative to reduce the carbon footprint of fossil fuels, yet their full economic and environmental performance remains unclear. Here, the production of renewable petrol from electrolysis and co-electrolysis-based processes is critically assessed, combining a palette of tools encompassing process simulation, costing evaluation, life-cycle assessment, and uncertainty analysis. Our results show that electrofuels are currently very expensive (10.4-fold higher cost compared to petrol), even when considering externalities (indirect cost of environmental impacts). Electrofuels could become cheaper than the fossil analogue, yet this would require relying on low-cost renewable electricity, which may find alternative uses. From an environmental perspective, we found that despite reducing the carbon footprint of the fossil counterpart, electrofuels could exacerbate impacts on human health due to burden-shifting. Overall, our work highlights the need to embrace impacts beyond climate change to ensure a comprehensive assessment of alternative fuels, and to monetise them to underpin a fair comparison with the fossil analogue.