When I saw the plastic vent I thought it was a high-efficiency water heater. When I saw the compartment covering the burn chamber I thought it was sealed combustion. It’s not. When you open the compartment (no gasket/seal) you’re looking directly at a conventional burn chamber access cover, but with various other equipment.
As you can see from the energy label, it’s not even close to high-efficiency, so why does it have a plastic vent and all these other components in the compartment covering the burn chamber? Looks expensive. You could get this kind of performance from a conventional water heater.
Might the reason be be limited room for conventional venting?