Energy Supply & Demand
Learn how energy supply and demand drive commodity prices using tightness, spare capacity and inventories. Includes diagrams, teaching notes, checklist and FAQs.
Table of contents
Key takeaways
- Energy prices respond to changes in expectations about supply and demand.
- Tight markets amplify moves because there is less buffer.
- Most short-term trading is about surprises versus what was priced in.
Visual map
Use the diagrams to translate the narrative into a simple question: what changed versus expectations, and does it make the market tighter or looser?
Key concepts (with meaning and application)
Each concept is written as a practical trading tool: definition → why it moves prices → how you use it.
The marginal barrel
What it means: The last unit of supply/demand that balances the market and sets the price.
Why it matters: If marginal supply is scarce or expensive, price must rise to ration demand or attract supply.
How to apply it: Ask: what is the marginal source today (OPEC spare capacity, US shale, inventories)? Trade the driver that changes that marginal source.
Spare capacity
What it means: Unused production capacity that can be brought online relatively quickly.
Why it matters: Lower spare capacity means the market has less shock absorption, so risk premia and volatility rise.
How to apply it: When spare capacity is tight, size down and expect larger reactions to data and headlines.
Inventories as a buffer
What it means: Stored energy that can temporarily offset supply interruptions or demand spikes.
Why it matters: Low inventories reduce the buffer, so the same surprise creates a larger price move.
How to apply it: Compare inventory levels and direction (draws vs builds). Persistent draws usually support prices.
Demand sensitivity
What it means: How demand changes when price changes (and when growth slows).
Why it matters: If growth weakens or prices are high, demand can fall, loosening the balance and pressuring prices.
How to apply it: Overlay macro signals (growth, PMIs, transport activity) to judge whether demand is strengthening or fading.
How to apply this to trading
Step-by-step approach
- Start with a simple question: is the market tight or loose?
- Identify the new information (data, policy, geopolitical headline).
- Decide whether it changes supply, demand, or risk premium.
- Translate into a trade: tightness improving (bullish) vs deteriorating (bearish).
Example
If inventories are drawing faster than expected and spare capacity is low, even a small supply disruption can trigger a sharp rally. In that environment, momentum moves can extend, but whipsaws are common on headlines.
Common mistakes
- Trading the headline without checking what was already priced.
- Ignoring the buffer (inventories/spare capacity) and being surprised by volatility.
- Treating one data point as a trend instead of looking for a multi-week pattern.
- Oversizing into news-driven markets where gaps and slippage are common.
FAQ
Why do oil prices move on forecasts, not only on actual supply changes?
Because markets price the future. If the expected balance changes, price adjusts immediately.
What does a ‘tight’ energy market mean?
It means low spare capacity and/or low inventories, so shocks cause bigger moves.
Is demand or supply more important?
It depends on the regime. In tight markets, supply shocks dominate. In weak growth regimes, demand expectations can dominate.
Summary
- Commodity prices are driven by supply, demand, inventory, and expectations.
- Watch the key marginal driver: production decisions, storage, weather, and global growth.
- Manage risk around scheduled reports and sudden supply shocks.
Last updated: 2025-12-28 (UK time).