Which aspect is crucial for a Transmission Service Provider to consider when selling ATC?

When a Transmission Service Provider (TSP) is selling Available Transfer Capability (ATC), it is essential to consider the available capacity after non-firm sales. ATC represents the maximum amount of electric power that can be transferred over the transmission system while maintaining reliable operation. To ensure that the system remains reliable and that existing firm obligations can be met, a TSP must carefully account for the capacity that is still available after accounting for any non-firm sales.

Non-firm sales are transactions where power can be sold without the guarantee of delivery, depending on system conditions. When estimating ATC, the TSP needs to subtract the capacity reserved for these non-firm transactions, as they could potentially impact the ability to deliver firm service commitments. This ensures that the TSP does not overload the transmission system and maintains reliability, which is critical for both regulatory compliance and customer satisfaction.

By understanding the remaining capacity after these sales, the TSP can make informed decisions about how much ATC is available for additional firm transactions, thereby optimizing their operations and ensuring that reliability standards are upheld.