When installing electrical appliances, keep in mind that most standard home electrical circuits are on a 120-volt line. Conventional outlets have two places to plug in devices and are called duplex outlets.

It's also important to note the quality level of your appliance(s) because the labor cost for installing more expensive equipment will be higher than for less expensive appliance(s).

Appliance Power Requirements
Check the power requirements of each appliance. To run major appliances and heavy electrical equipment, you need 220-volt current in the house. And unless your clothes dryer runs on gas, it will require a 220-volt outlet to operate, so it's necessary to upgrade to 220 to handle these and other heavy equipment.

Appliance Installation
When having an appliance installed be sure it can be removed easily for service. Flexible hook-ups for dishwashers and gas ranges can make repair jobs less labor intensive. Also, leave extra electric cable when installing electric wall ovens and cook-tops. This will minimize the time the technician spends on the job and reduce the cost to you.
Some other appliance installation tips to keep in mind:

Dishwashers
If your kitchen floor is being tiled, make sure that it is tiled beneath the dishwasher or at least raise its flooring to the same height as the tiles. Once down, there may not be enough clearance to remove the dishwasher for servicing. The only alternative will be to lift the whole countertop off of the cupboards, a needless expense.

Wall Ovens
If you are installing a wall oven below countertop level, be aware that small children could be exposed to a burn hazard. Wall ovens do not have to conform to the same temperature standards that regular ranges do. This is because they are designed to be installed above counter height.

Washing Machines
When installing a washing machine, be sure water shut-offs can be reached easily. Also ensure the water hoses are long enough to remove the appliance when necessary. A floor drain may also be necessary should the water pump or motor fail.
Washing machines are designed to be used on solid flooring, like concrete. If it is being installed on a wooden floor, extra joist bracing may be needed. The mounting of an additional plywood section can also strengthen an existing wooden floor. Severe internal suspension damage can occur if used on unstable flooring.