Originally Posted by
mcjimbosandwich
I'd argue for the opposite as it's hard to nail it to 280W+/- 10W even under perfect conditions. It's the normalized power of the duration of the interval that matters. After all, by standard definition, you average power of a 60min long time trial is FTP, the power you use to determine all your training zones.
I have found it helpful to change my Powertap setting to give me more smoothing of the data (10 or even 30 sec smoothing) so it is easier to try to hold a certain power level for intervals.
My main point though was that a formula to give a one time power output (as the OP described) is meaningless and doesn't serve any training purpose.