The water-saving claim made in the commercial you mentioned may be accurate, depending on various factors. Generally, running a dishwasher efficiently with a full load tends to be more water-efficient than handwashing dishes in the sink.
Here are some points to consider:
Dishwasher water usage: Modern dishwashers are designed to be more water-efficient than handwashing. They use a specific amount of water for each cycle, typically around 6 to 16 gallons (22 to 60 liters), depending on the model and cycle selected. Dishwashers also have sensors that adjust the water usage based on the load size and soil level.
Sink water usage: When handwashing dishes, people often leave the faucet running continuously, resulting in a significant amount of water waste. On average, a faucet releases around 2 gallons (7.5 liters) of water per minute. If you wash dishes for 10 minutes, that could amount to 20 gallons (75 liters) of water or more.
Efficient dishwasher usage: To maximize water savings, it's important to run the dishwasher efficiently. This means waiting until you have a full load before starting the cycle. Running the dishwasher every night, even with a small load, can still be more efficient than handwashing if the dishwasher is optimized for water and energy usage.
Energy considerations: It's worth noting that dishwashers also consume energy, primarily for heating water and running the machine. However, in most cases, the energy used by a dishwasher is still lower than the energy required to heat water for handwashing.
In summary, running a dishwasher with a full load, even on a daily basis, can potentially save water compared to handwashing dishes in the sink. However, to maximize efficiency, it's important to use a water- and energy-efficient dishwasher and ensure that you're running it with a full load whenever possible.