Energy Calendar Spreads: Storage, Seasonality and Basis

A futures curve orders contract prices by delivery month

A futures curve is a same-time set of prices for several delivery months in one commodity family. The prompt contract is the nearest relevant month and a deferred contract expires later. A calendar spread compares two months of the same underlying family. This guide defines the spread as deferred minus nearby. Under that convention a positive value means the deferred contract is higher. Market screens and trading conventions may reverse the legs, so always save the actual formula instead of relying on a spread name.

Contango generally describes deferred prices above nearby prices, while backwardation describes nearby prices above deferred prices. A curve need not be a straight slope: nearby months can be backwardated while later months form contango, and seasonal humps are common. Do not reduce contango to an assertion that the market forecasts a spot-price increase. Carry, stocks, convenience, risk premium, season and delivery constraints can all contribute.

Carry and inventory services shape storable-energy spreads

In a simplified cash-and-carry relationship, an operator buys physical supply, finances it, stores and insures it, absorbs losses and later makes delivery. Those costs provide a reference for a deferred premium. Holding inventory also provides an operational service: it can bridge a production or refinery outage, meet a customer obligation and respond to unexpected demand. The concept of convenience yield represents that non-cash benefit. When the immediate service of stock is valuable, the nearby price can be relatively strong.

When storage has spare capacity, a sufficiently large deferred premium may encourage inventory accumulation and put pressure on the spread. As tanks or caverns approach a limit, marginal storage cost and operational difficulty can rise sharply, weakening physical arbitrage. Storage must also connect to the benchmark delivery location through available transport. A visible difference above a generic cost estimate is therefore not automatic risk-free profit.

Inventory and curve shape determine each other

High inventory often accompanies a smaller immediate scarcity value and contango; low inventory often accompanies strong immediate value and backwardation. That relationship is useful, but not a one-way law. A price spread changes the incentive to store and therefore future stocks, while expected future stocks feed back into today’s curve. Inventory of the wrong quality or in the wrong location may also be unavailable for delivery into the benchmark contract.

For crude, separate commercial stocks, strategic stocks, pipeline fill and floating storage, then reconcile refinery input, imports, exports and production. The EIA oil inventory guide decomposes the weekly stock change into a balance. For natural gas, distinguish working gas, base gas, capacity and withdrawal deliverability, then examine regional storage and pipeline connection rather than relying only on a national total.

These are hypotheses, not price-direction rules. Test them with data aligned by time and region.

Separate gas seasonality and oil location basis from a time spread

A natural-gas curve can reflect winter heating, summer power burn, injection season and pipeline maintenance, making each calendar month a materially different demand period. A winter premium is not a confirmed cold-weather forecast; it can include capacity value and a risk premium for extreme demand. Storage smooths the seasonal difference, but injection and withdrawal rates and regional capacity prevent perfect arbitrage. The weather, storage and pipelines guide owns the physical gas balance.

Crude curves can also reflect refinery maintenance, driving and heating-fuel seasons, production cycles and shipping schedules. A difference between WTI and Brent, or between a pipeline hub and a coastal grade, is nevertheless not a calendar spread. It contains location and quality basis. Keep M2 WTI minus M1 WTI separate from same-month Brent minus WTI, and separate both from a crude-product crack. The refining and crack-spread guide takes the conversion spread.

• Time: Is the commodity and delivery point the same while only the month changes?
• Location: Does the delivery point differ even though the period matches?
• Quality: Do density, sulfur, heat content or other specifications differ?
• Conversion: Is there a refinery or power-generation step between the two products?
• Contract: Do settlement, delivery, lot size and last trade follow the same method?

Separate roll yield from spot return, a curve view and a CFD adjustment

A long position that sells a nearby future before expiry and buys a deferred future generally moves into a higher-priced contract in contango, creating an adverse roll relationship in price or quantity terms; backwardation can reverse that relationship. Total return still depends on the futures price changes while held, changes in curve shape, roll date, selected contracts, transaction costs and return on cash collateral. The initial curve cannot lock in the future roll yield.

Spot return, futures return, an excess-return index, a total-return index, an ETF and a CFD can all use different calculations. A CFD is a contract with a provider, which may apply a cash adjustment, splice a continuous reference series or charge separate daily financing when it changes the referenced future. This article does not generalise those provider terms; it explicitly hands CFD roll adjustment to the existing commodity CFD futures-curve and rollover guide. The current symbol specification and provider notice remain controlling.

Preserve a curve snapshot and connect it to position risk

A reproducible curve table stores each official contract symbol, observation timestamp, settlement or last price, currency, unit, delivery point, first and last trade, and physical or cash settlement. Put the formula, such as deferred minus nearby, in the spread-column header. If intervals differ, retain the day-count assumption behind a monthly or annualised comparison. Keep raw contract settlements even when a continuous chart is used for convenient visualisation.

1. 01Fix the contract

   Record underlying, location, quality, lot, month and settlement from specifications.

2. 02Capture one-time curve

   Align the price side and timestamp across every contract month.

3. 03State the spread formula

   Name both legs, subtraction order and number of calendar days.

4. 04Overlay carry and season

   Separate finance, storage, insurance, loss, inventory and demand period.

5. 05Remove other basis

   Keep location, quality and conversion spreads outside the calendar spread.

6. 06Stress the position

   Vary curve shift, twist, roll date, gaps and liquidity against a loss budget.

Verify lot, point value and expiry in the CFD contract-specification guide, while the risk-per-trade guide provides a general route from loss budget to size. If Backtest & Robustness Lab is used, document continuous-series adjustment, roll rule and costs. A historical stitched series must not be treated as the price history of one physical contract.