A prototype Rotor crank arm-based power meter was unveiled at last year’s Eurobike but this year’s show saw the Spanish firm reveal the finished article.

Rotor Power is now ready for production and is expected to arrive in the UK in December 2012 with a price tag of approximately £1,500. So what makes it different to other power meters?

The power meter is effectively two-in-one, in that each crank arm houses four individual strain gauges. That allows for the accurate measurement of power in each crank arm, so the rider will learn their individual left and right leg power outputs. Rotor claim their system is accurate to +/- two percent.

Rotor Power’s accurate left-right power readings make a range of additional data sets available to the rider, including torque efficiency – a reading which shows the positive v negative torque per leg, effectively showing the extent to which your legs are working against each other – and pedalling smoothness.

The headline weight of 556g (for the power meter alone, without chainrings or bottom bracket) makes Rotor Power the lightest crank-based power meter on the market and it carries just a 30g weight penalty over Rotor’s existing 3D+ MAS cranks. MAS (Micro Adjust Spider) allows the company’s Q-Rings to be fitted at finer increments.

The cranks use Rotor’s 30mm universal bottom bracket axle, which will allow it to be installed on almost any bike. Otherwise, the system is ANT+ compatible, so the power data can be transmitted to a Garmin Edge device, for instance, while the battery is user replaceable and claimed battery life is 300 hours.