Consistent, yes. A power meter, no. Here is the honest math.
Monsoon Cycles, Colorado Springs · Updated August 21, 2026
Virtual power estimates watts from your rear wheel speed using a resistance curve for your trainer. Zwift called it zPower; ours works the same way and the curves are published.
Against a real power meter, a well-set-up virtual power number typically lands within 10 to 15 percent. Sometimes closer. That sounds bad until you remember what training actually requires: not a laboratory-true number, but the SAME number for the same effort, week after week. Virtual power delivers that if you control the three things that move it.
Tire pressure: check it every ride, same number every time. Roller tension: same clicks against the tire every time; this is the big one. Warmup: a cold tire on a cold roller reads different from ten minutes in, so let it settle before judging an effort.
Get those consistent and your threshold test from March compares honestly to the one in June, which is the entire job. What virtual power cannot do is compare you to someone else's meter, which is why our leaderboards show the source of every ride's power.
Two setup details decide everything: pick the curve that matches your trainer (the brand guide) and get the wheel circumference right, because a 2 percent circumference error is a 2 percent speed error before the curve even runs.