Business Energy Glossary
What is the gas year?
The UK gas year runs from 1 October to 30 September each year. The cycle is chosen to align with the natural seasonality of UK gas demand: high consumption in winter (October to March) followed by lower consumption in summer (April to September). Gas industry pricing, Annual Quantity reviews, capacity allocations, and many contract structures all align with the gas year cycle. Understanding the gas year helps when interpreting contract terms, AQ updates, and seasonal pricing.
The gas year is a fundamental concept in the UK gas industry but unfamiliar to most customers because it does not align with the calendar year or the financial year. Bills are typically issued by calendar month but underlying industry operations follow the gas year cycle.
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What the gas year is
The gas year is the standard annual cycle used by the UK gas industry. It runs from 06:00 on 1 October to 06:00 on 1 October the following year. The gas day starts and ends at 06:00 each morning, reflecting the demand profile (overnight consumption is typically lowest, with the daily cycle running from morning to morning).
The gas year is sometimes referred to as the “winter-summer” cycle:
- Winter (1 October to 31 March). High consumption period driven by heating demand.
- Summer (1 April to 30 September). Lower consumption period.
Why this cycle is used
The October to September cycle reflects UK gas demand patterns:
- Demand peaks in January and February when heating loads are highest.
- Demand troughs in June, July, and August when heating is not required.
- Storage facilities are typically full at the start of the gas year (1 October, after the summer refill period) and reach minimum levels at the end of winter.
- The cycle aligns with the natural rhythm of supply procurement, hedging, and capacity planning.
The corresponding electricity industry cycle is the financial year (1 April to 31 March), reflecting the different demand seasonality of electricity (broadly flatter across the year with summer cooling and winter lighting both contributing).
Gas year and AQ updates
Xoserve updates the Annual Quantity for every UK gas supply point on 1 October each year, at the start of the new gas year. The update:
- Recalculates AQ from the previous gas year actual consumption.
- Applies weather-adjustment.
- Publishes the new AQ in the central Xoserve database.
Suppliers use the new AQ for pricing and contract band allocation for the upcoming year. Customers near AQ band boundaries may see contract price changes as a result of the October update.
Gas year and pricing
Gas industry pricing follows the gas year cycle in several ways:
- Winter and summer baseload prices. Wholesale market trades winter-only and summer-only products reflecting the seasonal demand difference.
- Capacity charges. Many capacity charges align with gas year cycles, particularly for DM customers.
- Storage withdrawal scheduling. Storage facilities fill during summer and withdraw during winter.
- Hedging strategies. Procurement programmes typically hedge winter and summer separately.
Gas year capacity allocations
Network capacity on the NTS is allocated for gas year periods. Shippers bid for capacity to feed into specific entry points and offtake from specific exit points across the upcoming gas year. The capacity auction takes place ahead of the gas year start.
For customers, this capacity allocation is invisible but underpins the supplier ability to deliver gas to the meter. Capacity charges are recovered through the unit rate and standing charge.
Gas year in contracts
Business gas contracts can be structured to align with various cycles:
- Calendar year contracts. 1 January to 31 December. Familiar but creates partial-winter and partial-summer exposure.
- Financial year contracts. 1 April to 31 March. Aligns with UK financial reporting but cuts across summer.
- Gas year contracts. 1 October to 30 September. Aligns with industry pricing and AQ cycles.
- Custom periods. Any 12-month or longer period agreed between customer and supplier.
The choice of contract period affects how the customer is exposed to seasonal price movements at renewal. Gas year contracts simplify the supplier hedging position but may not align with customer planning cycles.
the gas year FAQs
What is the UK gas year?
The annual cycle used by the UK gas industry, running from 1 October to 30 September the following year. Chosen to align with the natural seasonality of UK gas demand: high winter consumption followed by lower summer use.
When does the UK gas year start and end?
1 October to 30 September. The gas year starts at 06:00 on 1 October because the gas day starts at 06:00 each morning, reflecting the overnight low-demand period.
Why does the gas year start in October?
It aligns with the natural rhythm of UK gas demand and supply: storage facilities are full at the start of October after the summer refill period, and winter demand begins to rise from October onwards.
How does the gas year relate to my contract?
Business gas contracts can run on calendar year, financial year, gas year, or custom 12-month cycles. Gas year contracts align with industry pricing and AQ updates; calendar year contracts are more familiar to customers but may not optimise pricing.
When is AQ updated?
On 1 October each year, at the start of the new gas year. Xoserve publishes the new AQ for every supply point and suppliers use it for pricing and contract band allocation for the upcoming year.
What is the winter gas season?
1 October to 31 March: the high-demand period driven by heating loads. Winter gas prices typically trade at a premium to summer gas prices in the wholesale market.
What is the summer gas season?
1 April to 30 September: the lower-demand period when heating is not required. Storage facilities typically refill during this period, and prices are typically lower than winter prices.
Does the gas year apply to electricity?
No. The UK electricity industry uses the financial year (1 April to 31 March) for most annual cycles. Each fuel uses the cycle that best fits its demand seasonality.