Zero Price Hours

Zero price hours are settlement periods in which the wholesale electricity price clears exactly at 0 per megawatt-hour, or the local market equivalent. They typically arise when low-marginal-cost generation is sufficient to meet demand and the system has little remaining scarcity value for additional output.

Although less extreme than negative prices, zero price hours still carry an important market signal. They indicate that incremental generation in that interval has little economic value, often because renewable output is high, thermal units are inflexible, or transmission and storage cannot absorb more energy efficiently.

Key Aspects of Zero Price Hours:

• Indicator of Saturated Low-Cost Supply: Zero prices usually mean the market can meet demand using resources with very low marginal cost. Additional generation is not scarce, even if it is not yet penalized with a negative price.
• Frequent in Renewable-Rich Systems: Markets with high solar or wind penetration often see growing numbers of zero price hours during periods of strong resource output. Midday solar peaks are a common example.
• Operational Context Matters: Limited interconnection, insufficient storage, weak demand flexibility, or generator inflexibility all make zero price hours more likely. The same renewable volume may produce very different price outcomes in a more flexible system.
• Revenue Consequence for Generators: A high count of zero price hours lowers average realized revenue, especially for technologies that produce heavily in those same intervals. That makes capture price analysis more important than average annual market price alone.
• Useful Transition Metric: Tracking zero price hours helps quantify how often surplus low-cost energy appears in the market. It is a practical indicator of rising flexibility needs and of changing economics for renewable investment.