California electricity market (CAISO)

• California is a heavily populated state that is divided into two major zones: NP-15 and SP-15.
• Most of the year, the daily temperatures are moderate to warm. However, the dense population and hot summers can cause spikes in the electrical loads due to a demand for air conditioning.
• One of the major transmission lines, Path-15, bisects the state into two approximately equal parts and has given its name to the two major zones: NP-15 and SP-15.
• NP-15 (North Path 15)
• Covers the northern part of the state (San Francisco Bay area), north of Path 15.
• When rainfall or melting snow allows, this region imports low cost electricity from the Columbia River Basin in Oregon.
• For the remainder of the year, natural gas plants, supplied primarily from western Canada, set the price of power in NP-15.
• SP-15 (South Path 15)
• South of Path 15, the pricing zone for most of Southern California.
• A major importer of power from Arizona (natural gas and solar power) and Nevada (hydropower from the Colorado River).
• Natural-gas-fired plants in the south are fed from supplies in the rocky Mountain and West Texas regions.
• ZP-26
• A large but less important pricing zone that has a relatively low population and excess generation capacity.
• It connects to both the NP-15 and SP-15 zones.