A few weeks back United Airlines published the seat map of their new low density B787-9 configuration, leaving tongues wagging for the exceptionally large premium, and by contrast small economy cabins.
Absolutely, it's part of the calculus, but it's still quite small of an impact plus there are several more considerations other than seat weights, e.g. probably needs 1 less cabin crew, less potable water, etc. In terms of the seats, the business class seats will weight more (80-90kg), but people often forget it's the net weight, so 65 fewer economy seats (at 11kg each) so -650kg, 14 more premium economy (+- 20kg) so +280, and 16 more business (lets call it 90kg), so +1440kg, meaning net +880kg. That still small compared to the net decline in passenger weight.
What about the extra weight of a business class seat vs an economy one though? That could ad quite a few kg per passenger, right?
Absolutely, it's part of the calculus, but it's still quite small of an impact plus there are several more considerations other than seat weights, e.g. probably needs 1 less cabin crew, less potable water, etc. In terms of the seats, the business class seats will weight more (80-90kg), but people often forget it's the net weight, so 65 fewer economy seats (at 11kg each) so -650kg, 14 more premium economy (+- 20kg) so +280, and 16 more business (lets call it 90kg), so +1440kg, meaning net +880kg. That still small compared to the net decline in passenger weight.