Vehicle-to-grid EVs could slash electricity, driving costs

A new study suggests that widespread adoption of vehicle-to-anything (V2X) electric vehicles (EVs) could double as home energy assets, helping South African households save on fuel and electricity.

The research shows that combining EVs with rooftop solar not only reduces costs but also makes electric driving more competitive with petrol vehicles.

The study, led by University of Pretoria researcher David R Walwyn, examines the techno-economic interplay between small-scale embedded solar installations and battery electric vehicles (BEVs) equipped for vehicle-to-grid (V2G) interaction − a core component of V2X systems that allow energy to flow between vehicles, the home, or the grid.

V2X technology enables real-time communication between vehicles and their surroundings, including other vehicles, infrastructure, pedestrians and networks.

According to the research, this capability could make EVs more affordable for households, while also easing pressure on SA’s stressed national grid.

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“Battery electric vehicles with vehicle-to-grid capability achieve cost parity with households operating internal combustion engine vehicles.”

Charging EVs directly from rooftop solar significantly reduces transport and electricity expenditure. By substituting petrol or diesel with self-generated electricity, households benefit from lower marginal driving costs, while improving solar utilisation, the study finds.

“When charged from small-scale embedded solar generation, battery electric vehicles reduce both grid-based electricity demand and travel costs,” the authors write.

While EVs typically cost more upfront than petrol cars, electricity is far cheaper per kilometre than fuel. Charging from the grid already lowers travel costs, but charging from rooftop solar makes driving nearly “free”. The research also highlights that small-scale solar, when installed alone, remains expensive for most households.

“The levelised cost of electricity from small-scale embedded solar generation is approximately double that of grid-supplied electricity, and adding that surplus daytime generation is often poorly monetised or curtailed altogether,” the study says.

This cost imbalance limits the financial returns of solar unless households can store or shift excess energy − which is where EVs come in.

BEVs are essential to global decarbonisation roadmaps and are being increasingly adopted in many countries. However, significant techno-economic barriers remain before the adoption of BEVs becomes widespread in the Global South.

Issues include higher costs, grid instability due to high electricity demand during peak periods, lack of recharging infrastructure and restrictive driving ranges relative to internal combustion engines.

According to the study, vehicle-to-grid can play a critical part in load balancing (peak shaving) and reducing costs for BEV owners.

The study shows that the greatest economic benefit occurs when EVs can discharge electricity back to the home or grid, acting as mobile storage units. A fully charged EV, for example, could power a home for a full day or more, it notes.

“Bidirectional energy flows allow battery electric vehicles to act as mobile storage assets, enabling energy to be returned during periods of higher tariff value,” the research explains.

This approach increases the effective utilisation of rooftop solar, lowering its overall cost, while supporting household energy needs and the wider grid.

According to a studyled by research institute ETH Zurich and the Paul Scherrer Institute, EVs could become economically competitive across large parts of Africa well before 2040, driven by falling technology costs and the rise of solar-powered, off-grid charging infrastructure.

Off-grid solar-powered solutions will make EV charging possible even in places with no or unreliable electrical grids, it notes.

The authors emphasise that time-of-use pricing, bidirectional metering and V2G frameworks will be essential for scaling V2X in SA.

“Without these mechanisms, much of the potential cost savings and grid-support benefits of V2X would remain unrealised.”