V2L vs V2H vs V2G — definitions and boundaries

Three names, three very different things

V2L, V2H and V2G all describe energy flowing out of an electric vehicle, but they are not interchangeable. They differ in what the car talks to, what it feeds, and which rulebook applies. Getting the term right is not pedantry — it decides whether you are looking at a portable appliance, a notifiable fixed-wiring installation, or a grid connection that the network operator must be told about.

• V2L (vehicle-to-load) — the car acts as a standalone AC inverter (an AC generator), feeding portable appliances plugged straight into a socket or a Type 2 adapter. No grid handshake.
• V2H (vehicle-to-home) — a communicating bidirectional charger feeds the home's fixed wiring, typically through a changeover, usually during an outage or for load-shifting.
• V2G (vehicle-to-grid) — a bidirectional charger exports energy back to the public grid, running in parallel with it, to provide grid services or energy arbitrage.

V2L — the car as a standalone inverter

In V2L the vehicle's onboard power electronics run in reverse: the inverter turns the traction battery's DC into ordinary 230 V AC and delivers it through a built-in socket or an adapter that plugs into the car's Type 2 inlet. You plug appliances directly in. Critically, there is no high-level digital handshake with charging equipment or the grid — the car is simply acting as a generator. Output is typically in the 1.8–3.6 kW range on European models, though some vehicles export far more.

Because a V2L adapter draws power *out* of the vehicle rather than charging it, V2L sits outside the IEC 61851 charging-mode framework (Modes 1–4) and outside its control-pilot path — a V2L outlet is a separate vehicle-side AC output, not a control-pilot-mediated charging session.

V2H — a communicating bidirectional charger feeding the home

V2H is a different animal. Here a dedicated bidirectional charger is hardwired into the home and feeds the fixed wiring — typically through a transfer/changeover arrangement so the house can run from the car during an outage or on a schedule. This is not a dumb socket: it requires a managed, communicating discharge, which is where the ISO 15118 series — and specifically Part 20 — comes in. V2H readiness depends on both ends supporting Part 20, not just the car having a V2L socket.

On the equipment side, the DC bidirectional charging work in BS EN IEC 61851 (-23:2023 adds bidirectional power transfer for DC supply equipment; -24:2024 extends digital communication to discharging) is the technical foundation that makes safe, controlled V2H/V2G operation possible — again, distinct from a plain AC V2L socket with no negotiation.

V2G — bidirectional export in parallel with the grid

V2G goes one step further than V2H: the bidirectional charger doesn't just feed the home in isolation, it exports energy back to the public network, running in parallel with the grid for grid services or arbitrage. The moment a source can run in parallel with, or export to, the public supply, it engages the DNO's connection regime — ENA EREC G98/G99. G98 is the lighter, type-tested microgeneration route (within the small-generator threshold); G99 covers larger or island-capable installations, and is recorded as expressly treating a bidirectional EV as electricity storage subject to G99.

Where the boundary actually sits

Here is the line that matters, stated plainly: a plain V2L socket is not ISO 15118 and not G98/G99. It is the car acting as a standalone inverter for portable loads. It only crosses into the regulated world in two situations:

1. Wired into fixed installation — the instant a V2L output is taken into the home's fixed wiring (a changeover into the consumer unit, an inlet circuit, a sub-board), it becomes a BS 7671 installation matter and normally notifiable work — even though the car-side comms are still nothing like ISO 15118.
2. Run in parallel with the grid — the instant the arrangement can export to, or run in parallel with, the public supply, it engages the DNO regime (G98/G99). A true islanded changeover that physically cannot connect the two together is generally treated as a load and sits outside G98/G99 — but whether a given changeover genuinely prevents parallel operation is a design-and-test matter for the competent person and the DNO.

Why the distinction is practical, not academic

Marketing blurs these terms — a high-output V2L truck feeding a home integration system starts to look like V2H, and 'bidirectional' is used loosely. But the rulebooks are sharply different: a portable appliance under V2L, a notifiable fixed-wiring installation under V2H, and a DNO-notified grid connection under V2G. Confusing them is how people end up assuming a car with a V2L socket is 'V2H-ready' (it usually is not — that needs ISO 15118-20 at both ends and a bidirectional charger) or assuming an islanded backup needs a grid agreement (it generally does not, provided it truly cannot run in parallel).