This doesn’t make sense to me. You’re saying a water heater that uses N joules to heat water by 0.5N joules is 33% efficient? That would be difficult for most p

This doesn’t make sense to me. You’re saying a water heater that uses N joules to heat water by 0.5N joules is 33% efficient? That would be difficult for most people to translate: I use 100 wh to get 50 wh of heat, which should imply 50% efficiency. As the cost to gain the end state I want is what I care about.