How to exploit synergies between electric vehicles and buildings?

The electric vehicle is gaining market share. Its impact on the electricity system is still marginal, but in the future it will mobilize significant quantities of electricity that will have to be produced and transported. Vehicles will continue to be recharged mainly at home or in businesses. Individuals and businesses will pay the bill and the networks will bear the cost.

At the same time, solar roofs or shade structures will develop but will not necessarily produce electricity at the right time.

How can we ensure that this complex whole, made up of buildings, electric vehicles and decentralized electricity production systems, works best, in the interest of the electricity system and consumers, in order to make the electric vehicle even more attractive? The study by Équilibre des Énergies provides answers to these questions; it demonstrates the importance of the issues related to the optimization of vehicle charging and identifies the measures to be taken to promote it.

For Jean-Pierre Hauet, president of the Scientific Committee of Energy Balance and co-author of the study: "According to an Enedis survey from September 2024, two thirds of French people do not think about controlling the charging of their electric vehicle. However, it is a way to make the electric vehicle more competitive and reduce its impact on the network. It is absolutely necessary to encourage it because, in our opinion, it is the modern-day hot water tank!"

State of play

Driven by European regulations, light electric vehicles will represent almost the entire French fleet in 2050, or around 36 million units.

As a result, the electric vehicle will gradually become a major electricity consumption pole (67 TWh in 2050, according to the RTE study "Energy Futures 2050" of February 2022), particularly in buildings, exceeding the consumption associated with thermal comfort in homes (65 TWh in 2050, according to the same RTE study). At the same time, the growth in the production of renewable electricity, particularly from photovoltaic sources, will make significant quantities of electricity available, but not necessarily at the times when it is most needed.

Priority: recharging at the best time

There is a major interest in recharging electric vehicles at the right times by exploiting the synergies between electric mobility and buildings so that:

• producers and network managers do not have to oversize their infrastructures;
• suppliers can value electricity production at times when it is most abundant and least expensive;
• Consumers save on their energy bills by benefiting from favorable rates.

The first imperative is therefore to manage the recharge, drawing inspiration from what has been done for decades for hot water tanks. The Equilibre des Energies study shows that with simple price management, the French can save around €200/year, but two thirds do not benefit from it. Still according to Equilibre des Energies, more sophisticated management, accompanied by dynamic pricing, will save an additional €100.

To generalize tariff management, Équilibre des Énergies recommends:

• raise awareness among consumers, as part of the national sobriety plan;
• generalize and impose the technical specifications currently applicable to controllable terminals benefiting from the tax credit.

A major financial challenge for businesses

Optimal charging management must accompany the development of electric vehicle fleets. It is a way to play on the complementarity between the different types of vehicles, the consumption of buildings and to enhance solar contributions. This makes it possible to limit the impact on the network and the subscribed power. Employees can also benefit from optimized charging costs for charging their personal vehicles.

For Energy Balance, it is necessary that:

• Charging employees’ vehicles in companies during the day continues to be encouraged.

Preparing for the future: paving the way for restoring electricity to buildings or networks

Several players, including Volkswagen and Renault, are starting to offer formulas for returning the electricity contained in the battery to buildings (V2B) or the network (V2G). This is a way of taking advantage of the battery capacity desired for autonomy issues but which is not used daily.

The most accessible is clearly the development of V2B. The study shows that, combined with the management of solar panels, the savings made can offset 100% of the cost of recharging vehicles (i.e. around €600/year).

V2G is more delicate and will probably be reserved for professional fleets. But it could be part of the flexibility that the electrical system will need.

To pave the way for the return of electricity to buildings or networks, Équilibre des Énergies recommends:

• develop protocols for integrating the electric vehicle into the smart home and smart building ecosystem. Promote compliance with the ISO 15118-20 standard;
• complete ongoing studies on the impact of V2B and V2G on battery life;
• define the rules of access and use relating to battery data;
• lift restrictions on the reinjection of stored energy (regulation and excise);
• simplify the assembly of collective self-consumption operations to coordinate the management of recharging with photovoltaic production.

Illustrative image of the article via Depositphotos.com.