Three Winters in One Budget: A Board-Ready Energy Scenario Plan for 2026/27
Photo: Foreign and Commonwealth Office, OGL v1.0, via Wikimedia Commons
By early November, most UK organisations have a winter energy budget. Fewer have a plan for the winter they might actually get. A single central forecast is useful for planning, but it can obscure the range of outcomes that finance teams should be ready to manage. The practical response is not to predict the weather more precisely; it is to build a budget architecture that holds three plausible winters at once.
A single forecast is a promise the weather has not made
Winter energy costs move for two reasons that are often blurred together: price and volume. Price is shaped by wholesale gas and power markets, geopolitics, storage and the marginal cost of generation. Volume is shaped by the weather, occupancy, operating hours and the thermal performance of the estate. A mild winter can reduce consumption while leaving fixed charges untouched. A severe winter can lift consumption at the same time as wholesale prices react to strain in the system.
For a board, the useful question is not whether the central forecast will be right. It is how much variance the organisation can absorb, what would trigger a change in approach and who decides. That is a governance question as much as an energy one.
Degree days without the engineering degree
Degree days are a way of expressing how much heating or cooling a building is likely to need. For heating, the common UK base is 15.5°C. For each day, the difference between the base and the average outdoor temperature is added up. A cold day contributes more degree days than a mild one. Over a season, the total gives a rough measure of weather severity.
The useful step is to relate degree days to the site's own consumption. If a building uses more gas or electricity when degree days rise, that relationship can be estimated from historical data. Finance teams do not need a detailed engineering model to use the idea. They need a reasonable sense of how many kilowatt hours or therms move for each additional degree day, and a view on which sites are most exposed. A portfolio with electrically heated warehouses and poorly insulated offices will behave differently from a modern, well-controlled estate.
Three scenarios, one budget architecture
A workable scenario plan does not need dozens of variants. Three are enough to frame the conversation: mild, average and severe. The labels should be defined against the organisation's own baseline, not treated as national forecasts. A mild winter might be 5 to 8 per cent below the long-run average in degree-day terms; a severe winter might be 10 to 15 per cent above. The exact figures should be calibrated to the sites in question and reviewed against the last normalised heating season.
| Scenario | Weather assumption | Main budget effect | Management response |
|---|---|---|---|
| Mild | Below-average degree days | Lower variable consumption; fixed capacity and standing charges unchanged | Protect cash; avoid releasing all contingency too early |
| Average | Central degree-day assumption | Baseline budget | Monitor against normalised consumption |
| Severe | Above-average degree days | Higher consumption; possible wholesale price reaction | Trigger contingency; review hedging and operational controls |
The point of the table is not precision. It is to make the board's exposure visible before the season arrives.
How fixed and flexible purchasing behave
Fixed-price purchasing gives budget certainty on the unit rate for the volume covered. It does not remove weather risk entirely. If a site fixes its price but then consumes more than expected in a severe winter, the extra units are still bought at the prevailing price or under the supply contract's flex arrangements. Fixed purchasing is strongest when the organisation values certainty and has a good handle on volume.
Flexible purchasing behaves differently. It can allow the organisation to buy in layers and respond to market movements, but it exposes the budget to wholesale price risk and often to shape risk. In a severe winter, higher consumption and higher prices can arrive together, which is exactly when a purely flexible approach feels least comfortable. In a mild winter, flexible purchasing may look cheap in hindsight, but the budget should not depend on that outcome.
Most organisations sit between the two. The scenario plan should show what proportion of expected volume is fixed, what remains flexible and how each scenario changes the effective cost. A useful board summary is not a single blended price; it is a range with the hedged floor and the unhedged exposure clearly separated.
A board-ready framework in five steps
First, normalise the baseline. Use at least two years of consumption data where possible and adjust for known changes such as new sites, closures or altered operating hours. Second, estimate weather sensitivity by site or by portfolio segment. Third, set the mild, average and severe degree-day assumptions and translate them into consumption ranges. Fourth, map those ranges onto the purchasing position: fixed volume, flexible volume, pass-through arrangements and any take-or-pay obligations. Fifth, agree the contingency and the triggers for using it.
The output should fit on one or two pages. A board does not need a weather model; it needs a clear statement of the central budget, the severe-case exposure, the actions available and the point at which those actions are authorised.
Setting contingency without over-hedging
Contingency is not the same as hedging. A contingency reserve is a financial buffer for the severe case. Hedging is a purchasing decision that changes the organisation's exposure. Confusing the two can lead to over-hedging: fixing too much volume at a price that looks safe in October but becomes an opportunity cost if the winter is mild and consumption falls.
A sensible approach is to size the contingency to the severe case, then decide how much of that risk to remove through purchasing and how much to retain. If the organisation has limited tolerance for volatility, a higher hedge ratio may be appropriate. If it has strong cash flow and a diversified portfolio, it may prefer to retain more exposure and use operational measures, such as temperature set-point discipline and out-of-hours shutdowns, to manage the severe case.
The trigger points should be agreed in advance. For example, a review might be prompted if degree days run 10 per cent above the seasonal norm by the end of December, or if the flexible proportion of the book is more than a set percentage unhedged as winter peak approaches. Triggers turn a scenario plan into a decision tool rather than a theoretical exercise.
The November decision
A 2026/27 winter budget should be judged by how well it performs across the range, not by how closely it matches the central forecast. Finance and procurement teams that set three scenarios, separate price from volume, and define contingency and triggers before the cold arrives will be better placed to avoid both surprise and over-hedging. The winter will be what it is. The budget can still be built to meet it.
