New Home Power Requirements
Check your current electric or gas range wall outlet. Likely the wiring is already 120/240 volts.
If your current electric range is 120 volts, it will be plugged into or hardwired to a separate 120-volt outlet fed from a dedicated 120V circuit breaker. An additional 3-prong receptacle will be on the wall.
You will need only to purchase a new power cord for the electric cooktop, usually a requirement no matter what your current wiring set up. A gas cooktop should work well with the current set up provided you have gas utility service coming into the home.
Older Home Requirements
Check the electrical outlet. Is the current electric range hardwired to the power supply? Hard wiring is two or more actual wires leading from the wall power source to the stove wiring.
If it's hardwired, the voltage is most likely 120. You will need an electrician to install a new dedicated 240-volt circuit breaker in the breaker box then run a 240V line from the circuit breaker to the wall behind the stove where the 120 voltage is now located.
To make the proper voltage adjustments, a new wall outlet will be installed for the new cooktop. A gas cooktop could require a dedicated 120V circuit breaker and/or a line running from the breaker box to an outlet installed behind the stove to power the ignitor.
Power Source Location
The distance from the power source will largely dictate the amount of time it takes to complete the conversion and the cost to do it. In homes where the kitchens are located in the front of the house and the breaker boxes are located in the rear, the 240 volt line must travel from the back to the front.
The electrician will drill into an outside wood or brick wall located nearest the cooktop area to pull the line inside. He will then install an inside wall receptacle to plug in a new power cord leading from there to the stove.