Smarter Charging for Electric Car Sharing Could Drive a Greener Future
Cutting road transport emissions is no small feat, yet one promising approach is clear: fewer vehicles and more electric drive systems. Electric vehicles (EVs), when paired with car-sharing schemes, could dramatically slash traffic-related CO₂ emissions. But there’s a catch, the environmental benefit hinges on when and how those cars are charged.
A recent analysis by Empa, drawing on data from around 1.5 million users of the Swiss car-sharing provider Mobility, paints a revealing picture. Charging patterns matter. The researchers found that the cheapest charging windows and the greenest charging times rarely align. Those chasing the lowest electricity tariffs could save an average of 27% annually, while drivers prioritising climate-friendly charging could reduce emissions by up to 82%.
Study author Sven Eggimann summed up the challenge: “A key challenge is to combine cost and emission targets. Ideally, it should also pay off financially to charge electric vehicles in a climate-friendly way.”
Why Real-Time Tariffs Matter
The study underscores a simple truth: the environmental and cost implications of charging depend heavily on real-time electricity prices and CO₂ intensity. While Switzerland’s tariffs often feature only basic day/night price differences, the actual hourly fluctuations are far more nuanced.
Empa researcher Elliot Romano pointed out: “Most people in Switzerland don’t know what the actual electricity price or CO₂ emissions are at the moment of charging.” Without that information, optimising charging is tricky. Other countries, such as Denmark, have gone further by offering apps that display the current electricity price, enabling drivers to choose greener charging times.
However, expecting manual adjustments long-term isn’t realistic. The future lies in automation, smart charging systems that respond to real-time data and user preferences without constant intervention.
Incentives to Drive Behavioural Change
Data alone won’t spark widespread change. The Empa team found that incentives such as CO₂ pricing or variable tariffs tied to actual grid emissions could encourage greener charging habits.
Their simulations suggest that with a CO₂ price of roughly 30 cents per kilogram of CO₂ equivalent, it’s possible to align cost savings with emissions reductions, but only if tariffs reflect the true carbon footprint of electricity consumption.
Romano stressed: “Ideally, charging should be based on voluntary measures supported by incentives. These include, for example, cheaper electricity tariffs or reserved parking spaces during low-emission periods.” Without such incentives, more rigid approaches, like restricting access to chargers during peak-emission hours, may become necessary.
The Role of Car Sharing in Energy Efficiency
One of the strengths of car sharing lies in reducing the total number of vehicles in circulation. Even with high utilisation rates, the reduced fleet size eases pressure on the grid, especially during winter. Romano explained: “Car sharing requires less energy overall because there are fewer vehicles on the road.”
In Swiss cities, a 25% cut in car numbers could significantly reduce electricity demand during winter, when renewable generation is often lower. Shared cars also encourage mixed-mode transport, with users often turning to public transport or cycling for shorter trips.
Balancing Daytime Usage with Greener Charging
Shared cars are more likely to be driven during the day, which means overnight charging is still essential. Unfortunately, night-time electricity mixes tend to be less climate-friendly. Yet, according to Eggimann, the overall emissions profile of shared EVs remains competitive with private EVs, thanks to short charging stops and growing access to fast-charging points.
This opens up opportunities for strategically timing fast-charging sessions during low-emission windows, particularly as more renewable energy sources are integrated into the grid.
The Winter Challenge
The elephant in the room for Switzerland’s electrification strategy is the seasonal supply gap. Even with optimised charging schedules and fewer cars, Empa projects a winter electricity shortfall of around one terawatt hour per month by 2050. This gap won’t be bridged by battery storage or shifting charging loads alone.
Romano cautioned: “Electrification is therefore only part of the solution. If you really want to do something for the climate, you should rely on car sharing, public transport, and drive less overall.”
Moving Towards Integrated Smart Charging Systems
To unlock the full environmental potential of EVs in car-sharing schemes, charging infrastructure needs to evolve. Automation, real-time emissions data, and dynamic tariffs could create a seamless user experience where climate-friendly charging becomes the default, not the exception.
Eggimann envisions a future where “charging infrastructure automatically guides its users to low-emission and cost-effective charging times, without them having to constantly make decisions themselves.”
This vision would require close cooperation between energy providers, policymakers, and mobility service operators. Standards for smart meters, incentives for low-emission charging, and integration with renewable generation forecasting could make this a reality.
Building a Smarter Mobility Ecosystem
The road to sustainable mobility is about more than just electrification, it’s about optimising the system as a whole. Car sharing reduces the number of vehicles, real-time charging data makes low-emission charging possible, and automated smart charging ensures it happens without added complexity for the user.
If done right, this could mean cleaner air, lower emissions, and a more resilient energy system. As the Empa study makes clear, the technology is within reach, it’s the incentives and integration that will determine how quickly we get there.
