Actually:
· The water heater's rarely located right next to the washer. Add this up to a minimalized water intake and by the time the hot water reaches the machine, the intake valve shuts off. You'll end up with cold water in the washer, while using gas to heat your pipes ;-). · The fully-computer-controlled ones usually don't take water in, they 'sip' it, in order to reduce the water usage even further. (Take in a little splash of water, give the drum one spin to soak everything, repeat until sensors -> fuzzy-logic -> water_level="sufficient". Water usage is fully load-dependant!) That 'sipping action' can break some types of water heaters! · There /are/ some 'hot fill' models available on order. A niche, usually marketed for people with solar (water) heaters.