I'll start by saying I had my powertap SL+ serviced in early may and the internals were changed to the newer generation electronics... Previously my powertap zero offset never shifted (it changed when the firmware update messed up the numbers, and when it blew a torque tube in may otherwise it was *always* the same) since I got the new PT I manually zero every ride... whatever no big deal. When I zero the thing the zero offset jumps from 501 to 516 +/-1 and the power displayed seems to come up a bit, ~20 watts or so. Sunday was the district TT championships at Sattley. I went pretty well, I was feeling good on course, speed was good... but my power was lower than I expected. After the race it occurred to me that I'd warmed up on a different pair of wheels, I didn't manually zero! Average power was ~265 and normalized only a tad higher, my recent FTP sessions/tests at home and at essentially sea level have been suggesting an FTP of ~310. I knew from last year that I'd go faster on less power at Sattley (~4500ft) but I'd expected to be 10-15 watts above last years powers not 10-15 watts lower. It may have worked out because, while I knew I couldn't go a ton harder I did push a bit harder, especially on the way back and into the wind... I set a PR and earned the right to buy an NCNCA champion skin suit but I wish I knew my actual data.
