Installing a washer and dryer in a space that has not been previously set up as a laundry area requires hot and cold water plumbing lines; a drain line (called a standpipe) or a laundry sink where the washing machine's drain hose can discharge; electricity (120V for washing machines and 240V for most electric dryers); a vent and, if it's a gas dryer, a gas line. For a location less than 10' from the electrical panel and existing water lines, next to an exterior wall for venting, and with unfinished or rough walls (which do not require much finish work), total costs can be $350 -$600, depending on what exactly needs to be done and local rates.
However, total costs can be $700 -$2,000 or more if the desired laundry area is far from the current plumbing lines, electrical panel and exterior walls (for venting); if access is limited, such as plumbing pipes buried under a slab foundation; if there is no room to add additional circuits on the existing electrical panel; if the existing plumbing is aging or out of date; or if extensive work is required to make holes in and then restore finished walls or flooring. Just adding a new electrical outlet can cost $75 -$250 for a standard 120V line, or $300 -$800 for a new 240V circuit on the main electrical panel, while upgrading an electrical panel can cost $1,300 -$4,000. Professional installation of a new dryer vent averages about $200, but can cost $150 -$500. Installing a gas line typically costs $150 -$250 for 10 linear feet, and $300 -$750 for 20-30 linear feet, but it can be $800 -$1,000 or more for a complex installation in an area with high labor costs.
Installing a washer and dryer in an existing laundry room with all the necessary plumbing, electricity and vents already in place is typically a fairly straightforward project requiring only basic skills and tools and taking less than an hour. Many new appliance retailers include basic installation for free or for a $50 -$100 fee. A handyman might charge $25 -$150 depending on local rates and the amount of work required. DoItYourself.com explains how to install a washer and dryer.

What should be included:

All electrical and plumbing work must meet local building codes. The floor of the new laundry area should be level so the appliances will work properly. The hose connections and power cords should easily reach their sources without pulling, leaking or causing flow restrictions. Note that many appliances cords are short, and designed to be plugged into a nearby outlet. Never use an extension cord, especially on a dryer.

Additional costs:

Any electrical or plumbing work typically requires a permit from the local building or planning department. Depending on location and the extent and type of work being done, this can be free or cost $25 -$150 or more. Often a professional plumber or electrician will obtain any required permits as part of the project.

Shopping for a washer-dryer hookup:

Prices can vary significantly. If the project involves extensive plumbing and/or electrical work, get several estimates. If possible, get a written agreement that outlines the work to be done and the materials to be used.
Ask family, friends, neighbors or the staff at local hardware and plumbing store for a recommendation to a local plumber, electrician or handyman. For larger projects, search for local contractors through the Plumbing-Heating-Cooling Contractors Association or the National Electrical Contractors Association.
Request and check references; verify that they are properly bonded, insured and licensed. Check for complaints with the Better Business Bureau.