18-Inch vs. 24-Inch Dishwasher: Does Size Change Energy Cost?

An 18-inch dishwasher is not guaranteed to cost less to run than a 24-inch model. In WattCost's certified dataset, the overall dishwasher median is 239 kWh a year, or about $45 at the U.S. average electricity rate. Energy use depends on the individual model's water heating and drying design, not width alone.

Key takeaways

• The current database includes 68 certified dishwashers under 18 inches wide and 544 under 24 inches wide.
• The 239 kWh category median translates to about $0.21 per DOE-assumed wash cycle at the U.S. average rate.
• The annual figure assumes 215 wash cycles and includes energy for water heating.
• For an honest comparison, match capacity, cycle features, and the exact EnergyGuide kWh value—not just cabinet width.

Does a narrower dishwasher use less electricity?

A narrow dishwasher can be the right fit for a small kitchen, apartment, or bar area, but its width does not settle its energy use. Dishwashers use energy to circulate water, heat it when needed, and dry dishes. Those choices can vary sharply between two machines that occupy similar cabinet space.

The ENERGY STAR dishwasher criteria are expressed in annual energy and water terms, which is why annual kWh is the better shopping metric. The federal EnergyGuide label also reports a model's estimated yearly electricity use.

What does the certified dishwasher figure mean per cycle?

WattCost uses the 215-cycle DOE test basis for certified dishwashers. Dividing the 239 kWh category median by 215 gives roughly 1.11 kWh per test-basis cycle. At 18.83 cents per kWh, that is about 21 cents of electricity per cycle at the U.S. average rate.

That is a comparison estimate, not a promise for every program on your control panel. Heated dry, sanitizing options, water temperature, partial loads, and local utility rates can all change what you see on a real bill.

• Certified category median — 239 kWh/year
• DOE test basis — 215 wash cycles/year
• Median electricity estimate — about $45/year or $0.21/cycle

How can you choose between an 18-inch and 24-inch dishwasher?

Choose the width that serves your household and kitchen layout first. Then compare annual kWh within that size. A compact unit that must run more often because it holds fewer dishes can erase a small per-cycle advantage, while a full-size machine run half-empty can waste the capacity you paid for.

Browse narrow certified dishwashers and the complete dishwasher cost-to-run list before narrowing to a model. For the broader choice between using a machine and hand-washing, see WattCost's dishwasher comparison.

FAQ

Do 18-inch dishwashers use less electricity than 24-inch dishwashers? Not automatically. Cabinet width does not capture water-heating, drying, and cycle design. Compare the annual kWh listed for the exact models you are considering, then factor in how often each capacity would need to run in your household.

How much does a dishwasher cost per cycle in electricity? Using the current certified-category median of 239 kWh per year and the DOE 215-cycle test basis, the estimate is about 1.11 kWh or 21 cents per cycle at WattCost's current U.S. average rate. Your local electricity rate changes the dollar cost.

Does the dishwasher energy label include water heating? The certified annual figure used by WattCost includes the energy to heat water under the DOE dishwasher test basis. Actual household energy use can differ when you choose hotter cycles, heated drying, or a different number of cycles than the test assumption.

Where can I find efficient narrow dishwashers? WattCost lists certified dishwashers under 18 inches wide and ranks models by annual energy use. Use that list as a starting point, then confirm that the capacity, noise level, cycles, and installation dimensions suit your kitchen.

Data notes and sources

Every WattCost dollar figure in this guide is certified annual electricity use multiplied by the U.S. average residential rate in the site's current data snapshot. See the WattCost methodology for the formula, source data, and limits. Product-program context: ENERGY STAR dishwasher criteria.