Two types of wheels are 1) a passage where the energy production and the load are both outside the limits of the transmission system, and 2) a wheel outlet where the production resource is within the limits of the transmission system but the load is outside the transmission system. Wheeling often refers to the planning of the transfer of energy from one balancing authority to another. Since driving electrical energy requires the use of a transmission system, there are often associated fees that go to the transmission owners. In a simpler sense, it refers to the process of transmitting electricity through transmission lines. The fees associated with wheeling are called the «wheeling fees». This is an amount in $/MWh that the transfer owner claims for the use of their system. .