It appears as though the Hummer got caught up in the range to weight endless loop.
- Gotta have 350 miles
- Need to add more batteries
- Added weight reduced my range
- Need to add more batteries
- Repeat
I would expect the Rivian to be better if comparing equal weights of the vehicles just due to better aero. It seems that the Hummer gives no 'F's for efficiency, cause, well, it's a Hummer after all. Matching up a 100 kWh battery Rivian with a 100 kWh Hummer would not look well for the Hummer because it looks as though the body is built like a tank and as streamlined as a ham sandwich. The Rivian also uses 2170 cylindrical cells which are more energy dense in both volume and weight than LG's pouch cells used in the Bolt. The Ultium is supposed to weigh 25% less for the same energy than those used currently in the Bolt but will still be far behind the new 4680's IMO. The latest specs for the Rivian R1T are 400 miles with a 180 kWh pack.
But if you're considering the Hummer, and it appears as though it's targeting a demographic of off roaders, the efficiency is the least of your concerns. I think GMC made the right call and focused on the off roading capabilities rather than long distance touring. The only reason they probably went with the bigger battery to get as much range as they have is for towing.
It would be interesting to know what this behemoth weights though. I don't off road but I would think light weight would be an advantage but maybe traction is king. I would guess it would dethrone the Model 3 though as the safest vehicle you can buy.
As for the Cybertruck, it's certainly going to excel at efficiency especially with the new 4680 cells. If Rivian also goes with the 4680's then the contrast described above would be even larger. And if they too incorporate the pack (not the frame as much as the cells) as a structural member, better still. But again, talking efficiency when comparing the Hummer with anything probably misses the point.