Left side only power might not be as accurate due to leg imbalances, but it's still good enough for a lot of uses. I'm tracking my ride efforts, and using it for pacing. Not for structured training. I've gotten a pretty good idea of my best power at 1, 5, and 10 minute efforts. My power numbers have matched quite close on steady climbs to the calculated power for that speed on a few on-line bike power vs speed calculators.


For example, dcrainmaker.com posted this 30 second averaged chart, comparing Powertap hub, pedals, and chainring meters to the 4iiii left side meter. They track pretty close. (The 4iiii looks like it reads high on some peak efforts. I see this when going hard from a stop sign, sometimes getting high readings for a couple of seconds.)






And power readings jump around a lot from one second to the next. That's why bike computers show 3 second or 30 second averages. If my readings are accurate within 5% or so, that's good for me.

Here's a ride charted in the fantastic, free Golden Cheetah software. Each dot is a 3-second average.
Then, the Golden Cheetah Critical Power graph of this season's rides, with the best effort at all different time periods from 1 second to the longest ride time. The current ride shows as a line in the graph.