Average power is exactly what it sounds like: the average wattage produced over the course of a ride. The trouble is, average power isn’t necessarily a real indication of the work-rate you’re able to maintain. Yes, average power is affected by changes in terrain and wind resistance, but it doesn’t take into account the effects they have on your ability to produce watts.
That is, producing an average power of 250W for an hour’s ride on a flat road is a different proposition to producing a 250W average for 60mins in the hills. The figure may be the same, but the effort required is vastly different.
The harder you have to work to keep your wattage up, the greater the toll it’s going to take – and the quicker you’ll run out of steam. And since average power doesn’t take those physiological effects into consideration, it’s not the best reference to use when planning a pacing strategy.
And that’s where normalised power comes in. It’s like average power but a little more complicated. It calculates your average wattage, but incorporates adjustments for how your body responds to the different intensities of work. In other words, normalised power accounts for the cost of your exertions. As such, it gives you a figure that more accurately reflects the wattage you can realistically maintain for a particular ride, which makes it very important for pacing.