The comparison is between the amount of water the dishwasher uses (regardless of load) and how much water washing by hands uses. Dish washers use a surprisingly small amount of water (3 gallons per load on average). So the correct comparison is “do I run the sink long enough to consume more than 3 gallons of water when hand washing?” Chances are it’s slightly more efficient for you to run the dishwasher half full than hand wash.
The comparison is between the amount of water the dishwasher uses (regardless of load) and how much water washing by hands uses. Dish washers use a surprisingly small amount of water (3 gallons per load on average). So the correct comparison is “do I run the sink long enough to consume more than 3 gallons of water when hand washing?” Chances are it’s slightly more efficient for you to run the dishwasher half full than hand wash.