Energy Systems Catapult has used its Living Lab to examine how electric vehicle adoption could reshape electricity demand, finding that at around 48 per cent EV uptake the largest daily demand spike moves from early evening to the middle of the night. The analysis of 854 homes found the new overnight peak could be twice the size of the traditional evening peak, reflecting the influence of cheap charging tariffs. The work also includes a project with Scottish and Southern Electricity Networks that tested flexible use of EVs, heat pumps and storage heating in up to 200 households. Together, the findings make a persuasive case for targeted network reinforcement alongside locally responsive flexibility services.

A New Overnight Peak

Electric vehicles are becoming a material consideration for local electricity networks. Latest figures from the Society of Motor Manufacturers and Traders put the number of battery electric cars in use at approximately 1.8 million, a 34.7 per cent increase on 2024. As EV ownership rises, the timing and concentration of charging will matter as much as overall electricity consumption.

Energy Systems Catapult’s Living Lab uses real households with EVs and charging equipment to create a virtual community that can simulate higher levels of technology adoption. Its analysis identified a notable shift at around 48 per cent EV uptake, when cheap overnight tariffs draw enough charging activity into the same period to establish a new, much larger demand peak.

Claire Rowland, Senior Manager for the Living Lab and Whole Energy Systems Accelerator at Energy Systems Catapult, said:

“Data from Energy Systems Catapult’s Living Lab showed that at around 48 per cent EV uptake, the largest daily electricity demand spike shifted from the early evening to the middle of the night.”

The result is a useful reminder that a consumer proposition which works well at low adoption levels can have different network consequences when it becomes widespread. Overnight charging can help households access lower-cost electricity, but synchronised charging activity can create fresh pressure on local assets.

Local Conditions Matter

Electrification will not affect every part of the distribution network in the same way. EVs and heat pumps will increase electricity demand, but the impacts will depend on where technologies are installed, when they operate and the capacity already available within a particular area.

Adoption may be concentrated in streets served by the same transformer, even where neighbouring communities have much lower uptake. The local challenge can also arise from electricity export. In areas with high solar uptake, simultaneous generation on sunny days can raise local voltage and lead protective systems in equipment such as EV chargers to switch off.

Traditional infrastructure upgrades will remain essential in some locations. Yet physical reinforcement can be costly and may take years to complete. The Catapult’s work positions flexibility as an important complementary option, enabling networks to make better use of existing capacity by changing when electricity is consumed, stored or supplied.

Testing Household Flexibility

The Whole Energy Systems Accelerator, known as WESA, provides a testing environment that connects real household demand and controllable low-carbon technologies to a simulated local electricity network. This enables evidence from homes to inform assessments of network operation, market signals and consumer outcomes.

In northern Scotland, WESA worked with SSEN to test whether commercial flexibility services could spread household demand enough to support the retirement of some load managed areas. These areas have historically enabled the network to control the operation of certain electric heating systems, avoiding a large number of devices switching on at once.

The project used real electricity demand from up to 200 Living Lab homes, flexing EVs, heat pumps and storage heating before mapping that demand onto a virtual network. Different control and pricing methods were then tested to assess whether they could reduce peaks while maintaining acceptable outcomes for households.

Claire Rowland, Senior Manager for the Living Lab and Whole Energy Systems Accelerator at Energy Systems Catapult, said:

“The trial flexed EVs, heat pumps and storage heating in up to 200 Living Lab homes. Their real electricity demand was mapped onto the virtual network, allowing the project to test whether different control and pricing methods reduced peaks while still delivering acceptable outcomes for consumers.”

Signals Beyond National Prices

The research highlights a tension between national electricity price signals and local network requirements. A supplier may encourage overnight charging because electricity is plentiful across the UK, while a local substation may face overload if many vehicles respond to that incentive at the same time.

That distinction places value on flexibility arrangements which respond to conditions on individual networks rather than relying only on broad national signals. Flexibility could include delaying EV charging, adjusting heat-pump operation or using batteries to absorb electricity when generation is plentiful and release it when demand is higher.

Within the SSEN trial, a method described as dynamic congestion response, using day-ahead forecasting, performed sufficiently well for the network operator to propose it for commercial use. The work also indicated that flexibility can be delivered in social housing without compromising household comfort, an important consideration for fair participation in local energy services.

Evidence For Network Investment

Energy Systems Catapult’s findings show why decisions on electricity network investment need to consider technology, consumer behaviour and market design together. Modelling remains valuable, but real-world household data offers a stronger basis for identifying where flexible demand can release capacity and where grid reinforcement is unavoidable.

As EVs, heat pumps and solar become more common, the shape of electricity demand will continue to change. The Living Lab and WESA work provides a practical route for testing those changes before they become constraints, giving network operators clearer evidence for investment and flexibility decisions.