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ETH study: rooftop home solar panels can supply up to 90 per cent of the electricity for your electric car
by Martin Jungfer
Empa study: How can we make charging more environmentally friendly in future?
12.9.2025
Translation: machine translated
How can electric cars be charged in a way that benefits the climate and the bank balance? Researchers have analysed Swiss car sharing data. They argue in favour of technology, transparency and an incentive system.
Researchers at Empa and the University of Geneva have analysed the charging behaviour of electric cars using data from around 1.5 million users of the car sharing supplier Mobility. Over the course of the year, those who opt for the cheapest tariffs save an average of 27 per cent of the costs. Those who charge as climate-friendly as possible, on the other hand, can reduce emissions by up to 82 per cent.
According to the study, Switzerland produces and exports low-emission electricity from hydropower, especially when electricity prices are high. When prices tend to be low, electricity from fossil fuels is imported, which has a poor carbon footprint. Well done to those who have a photovoltaic system on their roof and can almost completely cover their vehicle's consumption.
Only a few benefit from this. More and more e-cars are coming onto the roads, which are dependent on public charging facilities. The car sharing study is therefore an example of a problem that needs to be solved. According to the simulations, climate-friendly and price-optimised charging could be combined with a CO₂ price of around 30 cents per kilogramme of CO₂ equivalent. Then the economic choice would no longer be the dirtier one. To achieve this, dynamic tariffs would have to reflect the real emissions of electricity consumption.
Costs and emissions barely known
«Most people in Switzerland do not know how high the price of electricity or CO₂ emissions actually are at the moment of charging», Empa researcher Elliot Romano is quoted in the press release. The study's calculations are based on hourly changing electricity prices. After all, while for a long time we only offered high and low tariffs for day and night, the first energy suppliers are now introducing dynamic electricity prices.
Other countries have already gone further: «In countries such as Denmark, users can see the current electricity price via an app and can consciously choose their charging times», says co-author Sven Eggimann. This works, but automated systems that can be customised to individual preferences and take the climate aspect into account are needed in the long term. This would require real-time information on electricity prices and CO₂ emissions.
Incentives are needed
As most people are persuaded by costs and convenience, the researchers recommend incentive systems. In addition to the calculated CO₂ price, reserved parking spaces at low-emission times or additional charges for «inflexible charging behaviour» could be further measures. Even car-sharing vehicles that are used a lot during the day would not necessarily have to be connected to the grid overnight, when electricity tends to be dirtier. «Short charging breaks and increasingly available fast-charging infrastructure leave sufficient scope for low-emission charging», says Sven Eggimann.
In the long term, the increasing demand for electricity from electric cars will be a major challenge, especially in winter, even with appropriate optimisations. For the year 2050, the simulation shows a deficit of around one terawatt hour per month in the cold season. «This seasonal supply deficit cannot simply be remedied with additional batteries or daily shifts in charging», Romano explains in the press release. «Electrification is therefore only part of the solution. If you really want to do something for the climate, you should rely on car sharing and public transport - and drive less overall.»
Header image: Shutterstock/Marc Stephan
Michael Restin
Senior Editor
Michael.Restin@digitecgalaxus.chSimple writer and dad of two who likes to be on the move, wading through everyday family life. Juggling several balls, I'll occasionally drop one. It could be a ball, or a remark. Or both.
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