There are several variables involved when it comes to the cost of installing a heat pump Washington. One factor that can have a great effect on the cost is the excavation of the ground. For instance, excavating through a concrete slab can be more expensive because of the difficulty associated with the task. Other things to consider are the cost of the heat pump unit, the installation cost, the required materials and supplies plus other fees for special equipment and tools. You also need to add the size of your home to generate a realistic cost for your Washington heat pump project. If your house is bigger, you will need a high capacity heat pump to cover your whole house. The higher the capacity of a heat pump in Washington, the higher the cost.