Regenerative Braking Energy Calculator

Regenerative braking uses the electric motor as a generator while slowing down, converting some of the vehicle's kinetic energy back into electricity stored in the battery instead of wasting all of it as heat in friction brakes. The energy available to recover is the vehicle's kinetic energy at the moment braking begins, and only a fraction of it is actually captured.

Kinetic energy equals one half times the vehicle mass times its speed squared: KE = 0.5 times m times v squared, in joules with mass in kilograms and speed in metres per second. This is the total energy the vehicle carries due to motion, the ceiling on what regenerative braking from that speed could recover.

Only a portion. The recoverable energy is the kinetic energy times the system's round-trip efficiency, which accounts for motor, inverter, and battery losses, plus any energy that must go to friction brakes. The efficiency depends on the vehicle and how hard you brake, so this calculator takes it as a user-editable input rather than assuming a fixed figure.

Kinetic energy scales with the square of speed, so the energy available to recover at a stop grows rapidly with speed. Braking from 60 mph offers four times the energy of braking from 30 mph. That is why regenerative braking returns the most energy in higher-speed deceleration and in stop-and-go driving with frequent slowdowns.

There is no single correct value; round-trip regenerative efficiency varies by vehicle, motor, battery state, temperature, and braking intensity, and hard stops shift more energy to friction brakes. Use a figure published for your vehicle or measured from your own data. Because it is system-specific, the calculator leaves efficiency as an editable input.