Yes that was with the 5$ USD option for shipping too. Not the 20$ option. Power is amazing, no more lying to myself.
More than not lying, it is useful !
Here's my most useful usage:
When you attack, you are clearly in the red for a moment.
But then, when you dropped everyone, keep the effort just below your critical power, you do not drain your battery anymore, but the dropped need to make the same effort you did to catch you.
The critical power is something you can evaluate with goldenCheetah an open source software I feed from my strava account.
Below the CP you recharge your battery, over the CP, you exhaust it.
And like everything in nature it is logarithmic !
And you have as well an estimate of your kJ reserve, and how deep you can dig before bonking.
A more pacific usage
is how fast you can do a long climb to insure you keep the same effort up to the top.