DM-i — BYD's hybrid system

The letters stand for Dual Mode, and the suffix marks the efficiency-focused branch of the family as opposed to the performance-focused one. In normal driving the car behaves like an extended-range vehicle: the engine turns a generator and the electric motor drives the wheels. Only at sustained higher speeds does a clutch connect the engine to the axle directly, where that is genuinely the more efficient path.

Why it matters when buying

The engine in these systems is designed for a narrow, efficient operating band rather than for wide flexibility, because it spends most of its life generating rather than responding to a throttle. That is why the fuel consumption figures look unusual against European plug-in hybrids of similar size, and why the driving character is closer to an electric car than the category label suggests.

For a buyer the relevant questions are the same as for any plug-in: electric range on the current test cycle, whether the battery accepts fast charging, and how the local tax and access rules classify the car. The architecture is interesting; the tax treatment is what shows up on the invoice.

Related: PHEV · EREV · blade battery