An average dishwasher draws around 10 amps. This number can range from 10 to 15 amps, depending on these factors: 

• Size and capacity of the dishwasher. Larger units and those with more features require more power. 
• Heating element. Efficient or powerful heating elements can increase amperage needs.
• Cycles and modes, such as heavy-duty or high-temperature washes

Modern dishwashers are designed for energy efficiency, which affects their amperage. Most U.S. residential dishwashers operate on a 120V circuit, and voltage compatibility can impact amperage ratings. 

Calculating the formula for a dishwasher power consumption

If you only have the wattage rating, you can estimate the current draw in amps by using Ohm’s law: Amps (I)=Wattage (P)/ Voltage (V). 

For example, a dishwasher rated at 1,200 watts operating at 120 volts would draw: I=1200W/120V=10A. This means the dishwasher ampacity will be about 10 amps.

Does the dishwasher need a dedicated circuit?

The National Electrical Code (NEC) usually requires a dedicated circuit for dishwashers in the U.S. This circuit should be either 15 or 20 amp for dishwasher, depending on its size and power requirements. 

A 15-amp circuit, using 14/2 NM wire with a ground, is suitable for smaller, compact dishwashers. The standard and more common option is a 20-amp circuit. It uses 12/2 NM wire with a ground and provides extra power for larger and more conventional dishwashers.

You also need to make sure that the circuit can handle the dishwasher's load without exceeding 80 percent of its amperage rating. Additionally, local electrical codes may have specific requirements for GFCI protection, and AFCI protection may vary by jurisdiction. So, you need to always consult local code authorities for precise guidelines on dishwasher circuits in your area.

The wiring of a dishwasher depends on a model.In many older setups, dishwashers are "hardwired" into a home's electrical system. This means they're connected directly to the house's wiring, not plugged into a regular wall socket. It's a strong connection but can be tricky if you ever need to move or change the dishwasher.

So, how to wire a dishwasher that is new? Newer dishwashers come with a cord and plug that fits into a regular wall outlet. This makes it simpler to install, move, or replace the dishwasher. But it's important to check if the outlet can handle the dishwasher's power needs.

What are dishwasher cables?

NM-B cables are the most common type of cables  used to feed dishwasher circuits. Most common sizes of these cables used for feeding dishwasher circuits are 14/2 AWG and 12/2 AWG. 

• NM-B (Non-Metallic Sheathed Cable). NM-B is commonly used to feed dishwashers in standard indoor, dry locations. It consists of insulated conductors within a plastic sheath and is appropriate for most residential dishwasher installations. NM-B is not suitable for wet or damp locations.
• UF-B (Underground Feeder Cable). UF-B cable is designed to withstand wet and damp conditions. It’s used for dishwasher installations in such locations as basements or outdoor kitchens. UF-B is also suitable for underground runs to power dishwashers.
• MC (Metal-Clad Cable). MC cable features a metal armor that provides mechanical protection. It’s not specifically designed for wet or damp locations, but it can be used in areas where there's a risk of mechanical damage. For example,it is suitable for dishwasher installations in industrial kitchens where heavy equipment and potential physical damage exist.

For internal and control wiring of dishwashers, manufacturers typically use specialized wiring and connectors designed for low-voltage and control purposes. These internal cables are specific to the dishwasher's control systems.

• Ribbon Cable. Dishwashers often use ribbon cables with flat, flexible connectors for internal control connections. These cables are well-suited for transmitting signals between different components of the dishwasher's control system.
• Control Board Wiring Harness. Dishwashers feature control boards that manage various functions. Manufacturers use custom wiring harnesses to connect the control board to sensors, switches, and other components within the appliance. These harnesses are tailored to the specific model and brand of the dishwasher.