Dishwasher Energy Use: kWh and Water Per Cycle vs. Washing by Hand

A modern dishwasher uses roughly 1 to 2 kWh of electricity and about 3 to 5 gallons (11 to 19 liters) of water per cycle, depending on the model and the cycle you pick. ENERGY STAR certified standard-size models sit at the low end of that water range. Washing the same load by hand under a running tap usually takes several times more water, so a full, efficient dishwasher is the thriftier choice in most homes.

How many kWh does a dishwasher use per cycle?

Most standard-size dishwashers use about 1 to 2 kWh per normal cycle, and the heaviest settings can go higher. The motor and pump draw very little. Most of the energy goes to heating water and, on many models, to a heated dry at the end.

Where that energy comes from depends on your plumbing. Some of the hot water arrives from your home water heater, so part of the cost shows up on your gas or electric water-heating bill. The rest is heated inside the machine by an element under the tub, which raises the water to wash temperature, often somewhere around 120 to 150°F (49 to 66°C) on normal and heavy cycles.

Settings that push usage up:

• Heavy, pots-and-pans or sanitize cycles, which run hotter and longer
• High-temperature wash or extra rinse options
• Heated dry, which runs an element after the final rinse
• Running half loads, which spends a full cycle’s energy on fewer dishes

Eco or energy-saver cycles often run longer than normal cycles. The extra time lets them use cooler water and soak food off instead of heating more water. If you wonder why an eco cycle takes three hours, our guide to typical dishwasher cycle times explains it.

How much water does a dishwasher use?

A standard-size dishwasher sold in the US today uses no more than about 5 gallons (19 liters) per cycle under federal efficiency rules, and ENERGY STAR certified models use less, roughly 3 to 3.5 gallons (11 to 13 liters). Compact models use less again because the tub is smaller. Older machines built before the stricter standards can use 8 gallons or more.

The machine reuses the same small amount of water many times. It fills the bottom of the tub, a pump sprays that water through the arms, filters catch food bits, and the water drains and refills only a few times per cycle. A tap pours fresh water straight down the drain the whole time it runs.

How much water does washing dishes by hand use?

Hand washing a full load under a running tap commonly uses 20 gallons (76 liters) or more. US kitchen faucets are allowed to flow at up to 2.2 gallons (8.3 liters) per minute, so 10 minutes of rinsing and washing can use about 22 gallons. ENERGY STAR estimates that an efficient dishwasher saves thousands of gallons a year compared with hand washing.

Most of that hand-washing water is also heated by your water heater. That makes hand washing an energy cost too, often a larger one than the dishwasher’s.

Is a dishwasher cheaper to run than washing by hand?

For a full load, an efficient dishwasher usually costs less than washing by hand with hot running water. The comparison changes in a few cases:

• You hand wash in two filled basins (one wash, one rinse) instead of under a running tap. This can use a similar amount of water to a dishwasher.
• You run the dishwasher half full, or pre-rinse every plate under hot water first.
• Your dishwasher is old and uses far more water and energy than current models.

Scraping food into the trash is enough for most modern machines. Pre-rinsing under the tap can add more water than the dishwasher itself uses. Many detergents are designed to work on food soil, and our comparison of dishwasher pods, powder and gel covers which types handle stuck-on food best.

How do you work out what a dishwasher costs to run?

Multiply the kWh per cycle by your electricity rate, then by the number of loads. A machine that uses 1.5 kWh per cycle at 16 cents per kWh costs about 24 cents per load in electricity. Run it five times a week and that is about $1.20 a week, or a little over $60 a year. Your own rate is on your utility bill, and it varies widely by state and time of day.

The yellow EnergyGuide label on a new dishwasher gives an estimated yearly kWh and cost based on a standard number of loads and a national average rate. If you know your model’s yearly kWh, the appliance electricity cost calculator turns it into a yearly cost at your rate.

If your water heater runs on gas, the electricity figure understates the total, because part of the hot water is heated by gas. The Department of Energy’s Energy Saver site has guidance on estimating appliance and water-heating costs.

How can you cut dishwasher energy and water use?

1. Run only full loads, loaded so the spray arms can turn freely.
2. Scrape plates instead of rinsing them under the tap.
3. Use the normal or eco cycle for everyday loads and save heavy cycles for baked-on pans.
4. Turn off heated dry and let dishes air dry, or crack the door open at the end of the cycle.
5. Clean the filter regularly so water circulates well and dishes come out clean the first time.
6. If the machine sits far from the water heater, run the kitchen tap until the water is hot before starting, so the first fill is not cold.
7. Run the dishwasher at off-peak hours if your utility charges time-of-use rates.

Hard water leaves film that can make you rewash dishes, which wastes a cycle. If you see cloudy glasses, see how to remove hard water stains in a dishwasher.

When does replacing an old dishwasher make sense?

Replacing a working dishwasher only to save energy rarely pays back quickly, because the yearly running cost of any dishwasher is modest. Replacement makes more sense when the old machine needs a costly repair, leaves dishes dirty so you rewash them, or is old enough to use well over today’s 5-gallon limit. When you shop, compare the yearly kWh on the EnergyGuide label and look for the ENERGY STAR mark.

Quick answers

Does heated dry use a lot of electricity?

Heated dry adds noticeably to each cycle because it runs a heating element after the wash. Air drying, or opening the door slightly at the end, avoids that energy.

Is it bad to run a dishwasher half full?

It does no harm to the machine, but you pay for a full cycle’s water and energy for fewer dishes. Some models have a half-load option that uses less.

Does a dishwasher use hot water from the water heater?

Most US dishwashers connect to the hot water line, then heat the water further inside the tub. Part of the running cost therefore appears on your water-heating bill.

Is the eco cycle more efficient if it takes longer?

Yes. Eco cycles trade time for heat, soaking food at lower temperatures, so they use less energy even though they run longer.