The planning challenge for City Light is to assure that there is enough, but not too much capacity to meet growth as it happens. Too much capacity means we're wasting money -- we've invested the dollars to provide the electricity but don't have enough customers to pay for it. Too little power means our customers won't have the reliable electricity they need to keep people at work.

And predicting demand is difficult. Changes in the economy can quickly alter the picture up or down. That's why flexibility in the system is critical.

How do we build flexibility?

What is a Substation? Electricity flows into a substation from high-voltage transmission or distri- bution lines. In the substation, the voltage is lowered and the electricity is routed to the overhead and under- ground distribution lines that feed our homes and businesses. Stated another way, substations act as "distribution centers" where power is received in bulk, broken down, and delivered to the end user. Substations contain transformers and complex switchgear, the number and size of which determine just how much power it can receive and send out, and how quickly. As the demand on a substation begins to consume its capacity, it needs to either be expanded or shift part of its load to another substation which has excess capacity. If expansion is not possible and no neighboring substation exists to accept the extra load, a new substation is required. Substations come in many forms. Some are completely open, others come encased in cement and still others are built inside existing buildings and are not visible.

A new substation currently planned for the Interbay neighborhood will help. It is approximately two years from completion. It will take some load off the primary substation now serving South Lake Union, but as the Mayor's vision unfolds, we'll ultimately need to add another substation closer to this new growth center. We don't know exactly when it will need to be ready or exactly where it should be located, but we do know that putting a substation in the middle of a busy city is hard to do.

A new substation doesn't rise within a few weeks. Planning must begin well in advance of the actual need. A substation needs nearly an entire city block, so property must be secured, environmental impacts determined, neighborhood groups and other interested parties consulted, and engineering designs completed. This process can take five years or more.

Flexibility will be paramount in planning for this new substation. We'll need a site that can accommodate a range of growth and capacity scenarios, and we'll build only what's needed when it's needed. We're also committed to principles that make us a good neighbor - no effect on housing and no taking of valuable open space. In fact, our principles call for us to be a net plus for the neighborhood.

Who pays for all this? The people who use it do. As a public utility overseen by the Seattle City Council, Seattle City Light sets rates to cover its operating costs only. Furthermore, our rates capture the cost of service to individual customers over time. The increased revenue from electricity consumed at South Lake Union will pay for the cost of the improvements. Plus, everyone benefits from the additional reliability that comes with a new substation.