Demand response and vehicle-to-grid: Engineering and performance

Fast to deploy, but capacity depends on people joining

What this tab covers Engineering and operating performance: round-trip efficiency, whether power and energy can be scaled separately, footprint and siting, and safety.

Flexibility is quick to deploy and needs no new sites, but its capacity is soft. It lasts only a few hours, depends on people taking part, and how efficient it is depends on whether energy is simply delayed, stored as heat, or exported from a car.

Round-trip efficiency

Mixed

Simply delaying load loses no energy, because the same energy is used later. Pre-heating or pre-cooling loses some heat through the building fabric, and V2G loses energy twice, in the charger and in the battery. None of our sources gives an efficiency figure for these losses. Efficient appliances add to the benefit. A Northwest US study found managed heat pump water heaters replacing resistance heaters removed about 90% of their evening peak, and LBNL cites managed EV charging peak reductions of up to 90%.¹¹³

Evening peak cut, managed heat pump water heaters about 90%¹ Peak cut from managed EV charging (literature) up to 90%¹³

Power and energy decoupling

Mixed

Power is the sum of the devices enrolled; energy is limited by comfort, tank size or how much charge drivers will spare. More capacity means signing up more customers, not buying more kWh. The best programmes enrol more than half of eligible devices. Smart charging alone has limited headroom because cars tend to arrive about 88% charged; V2G unlocks far more. Untapped potential is large: residential air conditioning drives about 600 GW of peak demand worldwide.²⁴⁸

Enrolment, best-in-class programmes 50%+² Average EV state of charge on arrival (German case) about 88%⁸ Global residential air-conditioning peak demand about 600 GW⁴

Footprint and siting flexibility

Favourable

No new site is needed. The resources sit in homes, factories and depots that are already connected where networks are stressed. V2G is still limited by products: only 22 vehicle models offer V2G, under 1.5% of EV models, and Chinese carmakers, despite making over half of EV models, offer only one model with commercial V2G (sold in a UK offer). China launched 30 V2G pilots in 9 cities in 2025 and aims for 5,000 V2G charging facilities by end-2027.⁸

V2G-capable models 22 (under 1.5% of EV models)⁸ China V2G pilots (2025) 30 projects in 9 cities⁸ China V2G target 5,000 facilities by end-2027⁸

Safety and thermal runaway risk

Mixed

Physical risk is low because no new energy store is installed. The risks are digital and electrical: the cybersecurity of millions of connected devices, interoperability between platforms, and safe export from cars during grid faults. IEA notes that the V2G standard ISO 15118-20 (2022) is implemented differently by different carmakers, so interoperability is very low, and grid codes vary by country. Static time-of-use tariffs can also make many cars switch at the same moment, which creates a new peak.¹⁸

V2G communication standard ISO 15118-20 (published 2022)⁸

Sources

Pathways to Commercial Liftoff: Virtual Power Plants US Department of Energy, 2023
Liftoff: Virtual Power Plants (2024 update fact sheet) US Department of Energy, 2024
Electricity 2026: Flexibility International Energy Agency, 2026
Global EV Outlook 2026: Vehicle-to-grid technology International Energy Agency, 2026
Are load flexible technologies affordable? A population-scale cost-benefit analysis (Grahovac et al., ACEEE Summer Study) Lawrence Berkeley National Laboratory, 2026