lightly lighter, less MOSFETs... just a little more efficient.
There's not really any significant evidence that this is true. In fact the 2020 Performance 18" (980) was notably
more efficient than the 2020 AWD 18" (990) in EPA testing. My theory is that it was tested with the fully updated full set of efficiency optimizations, while the 2020 AWD was tested with just the intermediate improvement (there were at least two separate efficiency improvements, one around the time of this testing). If they had had the same software I would have expected them to get roughly equivalent results.
You might even expect 33% more MOSFETS (24 vs. 18) to reduce losses in the FETs in the Performance (or older AWD through sometime in 2019) motor, though any such effect doesn't appear to be substantial and it's never really showed in any efficiency testing.
Better software
Better motors
Better battery chemistry
Better cooling and heating - heat pump for efficiency
Add them all up, and the range goes up by a whole lot
In terms of raw, best achievable efficiency, on a 2018, vs. a 2021, with heat pump off, there appears to be
no significant difference between these vehicles, assuming they are both on the latest software build. And the batteries appear to be the same nominal size. (Unless you're opting for a Performance of course.) So no substantial range change.
So it's not great to give people the impression that there is going to be a significant difference in range between these two vehicles. However, some reasons I can think of that a buyer might want to upgrade if range is a concern:
1) If your 2018 battery is degraded by 5-10%, you'll get that back.
2) You are in a climate where the heat pump would be helpful (rainy Pacific Northwest, for example) and save you money & efficiency. (This is the main reason for the increase from ~332 EPA miles (not 322) on the Performance 2020 18" to 353 miles on the 2021 AWD.)
I'm sure there are tiny optimizations and hardware changes that actually DO improve efficiency aside from the heat pump, but based on EPA test results they do not appear to be large. (2020 Performance 18" (980) is only about 2.5% less efficient on the raw UDDS test in the city and
identical efficiency (within 0.5%) to the 2021 AWD (990) on the HWFET test.)
So my opinion is that anyone buying a 2021 Model 3 AWD solely for the 14% range increase from 2018 is likely to be sorely disappointed (caveats noted above) - but of course there are many other reasons to just buy a new car if you have the money for it.
This one is certainly true.
I'm don't doubt you, but was curious about what specifically you're referring to when comparing the 2021 77.8kWh battery to the older 2018 77.8kWh battery in terms of better battery chemistry. The denser Performance batteries in 2021 are superior, for density, at least.