Determining the efficiency of a dishwasher depends on several factors, including the dishwasher's energy and water consumption, the number of dishes being washed, and the water usage when handwashing. Let's break down the considerations:
Energy efficiency: Dishwashers generally use less energy per load than handwashing. Modern dishwashers are designed to be more energy-efficient, using advanced technology to heat water efficiently and optimize the cleaning process. However, if you're only filling the dishwasher halfway, you're not taking full advantage of its capacity, and it may be less energy-efficient in this scenario.
Water efficiency: Dishwashers are also designed to use less water compared to handwashing. The amount of water used in a dishwasher cycle is generally regulated and optimized for efficiency. Filling the dishwasher only halfway may lead to less efficient water usage per dish.
Handwashing habits: Handwashing can vary widely in terms of water usage, depending on how you do it. If you leave the water running continuously while washing dishes by hand, it can be less water-efficient than using a dishwasher. However, if you fill up a basin with soapy water and another with rinse water and turn off the tap while scrubbing and rinsing, handwashing can be more water-efficient.
Considering these factors, if you and your roommate are only able to fill the dishwasher halfway in a day, it might be more energy and water-efficient to wash the dishes by hand, provided you adopt water-saving habits during handwashing. Here are some tips for water-efficient handwashing:
Use two basins: Fill one basin with hot, soapy water for washing, and the other with warm water for rinsing.
Turn off the tap: Avoid leaving the tap running continuously while washing and rinsing dishes.
Scrape excess food: Scrape off food scraps into the trash or compost before washing dishes to reduce the amount of water needed for pre-rinsing.
Wash full loads: If you have only a few dishes to wash, wait until you have enough for a full load to minimize the number of handwashing sessions.
In conclusion, if you can adopt water-saving habits during handwashing and make sure to wash full loads, it may be more efficient to wash dishes by hand in your current situation. However, keep in mind that advancements in dishwasher technology and energy-efficient models might still make dishwashers more efficient overall when used optimally with full loads.