If you take the 315AW unquestioned the 900w might just be a marketing "comparison indicator" how much power would be needed with the older v15 to achieve 315 AW. It is pretty close if you take the 230 AW Hepa version of the v15. 230 / 660 * 900 = 313,14.
It is also the same for the "first" AW rating of the gen5 of 262 AW (later changed to 280) : 262 / 752 * 900 = 313,56.
Possibly. Your calculations are just taking the ratio of air power to the power rating on the label, which is an efficiency rating, giving about 35% in all cases.
After some reading and digging—something you won’t find on cesspools like reddit, I think those labels represent the nominal power rating of the machine. Many countries require appliances to list a power rating on the label, often based on standardised tests (e.g., IEC 60335 for household appliances). For cordless vacuums, this might represent the maximum power draw under a specific load (e.g., Boost mode with a standard attachment, not necessarily the 100 W head).
I realised I’d cocked up the numbers earlier, so I’ve reattached. The powers are the estimated (so not accurate) drained by the machine from the battery in the specified usage mode and situation. The values for when on carpet include the 100 W power head, so the motor power (and other machine losses) will be 100 W lower. The run times are likely a bit higher than the machine reports, so these powers may also be slightly overestimated in all cases, particularly the highest values in Boost mode.
What’s generally true is that the nominal or peak power label rating is comparable to the peak power measured in Boost mode on all three machines—including the V16. Since the V16 lists a surprisingly lower nominal power rating of 450 W, this does indicate it has been reduced deliberately over the earlier versions. If it’s not the case that there’s some firmware cap currently there (e.g. by accident) and it has been designed with significantly reduced power in all modes like this deliberately, then it would suggest Dyson’s priority has shifted from performance to stopping customers complaining about runtimes, since this extends it. If that’s true, and I’ve no evidence there’s a software issue, then that’s just terrible and I’m going to absolutely hammer Dyson in the review. It would also suggest that 900 W motor thing is meaningless marketing, and in fact, I’m not even sure what it means in terms of real-world use. Dyson don’t usually market misleading crap. Maybe things have changed…I don’t know for sure yet, but I'm starting to smell some rot from all this data (note: not concluded from the rabid vacuum enthusiasts' wishful bile spitting).
You won’t get a straight answer out of Dyson customer services, who are just robot guard dogs, and the engineers who understand things are probably under a gagging contract so couldn’t speak freely and chime in with clarification, so we just have to take what we see as it is. This thing can’t clean for shit and is vastly outperformed by both the v15 and gen5. So, I’m back to my initial reaction: I can’t believe Dyson did this and if they genuinely did, I hope they get all the hate in the world from V16 customers who return them in disgust. From the moronic user reviews I’ve seen so far, I doubt most of them would even notice they’ve got a Dyson machine in their hand over any other product and are just thrilled it's shiny. What a way for Dyson to seemingly undermine its pioneering and genuinely amazingly interesting constituent technologies. For the first time ever, I'm geninely contemplating returning a Dyson product. I still believe they can software modify the power cap in auto mode though, so we'll see what happens in the next week or so.
