Does anyone know how accurate the calorie information is on the Nike+? I assume it is like gym equipment and is high by about 10-15%... but does anyone know?

My Nike+ calorie count is about 25% HIGHER than my hrm. I am on my second sensor and this sensor did not calibrate as well when I calibrated for distance, so I don't expect the calorie count to be accurate so I use the hrm info.