Weather and Energy Demand: Why the Forecast Moves Your Bill
Temperature, wind and sunshine help explain changes in energy demand and renewable generation. This two-day view covers ten Met Office sites across England, Scotland and Wales and gives context for the live electricity page, not a local weather forecast.
Why weather drives demand
Colder homes lose heat faster, so heating demand rises. Wind and sunshine affect how much low-fuel-cost generation is available at the same time.
The next two days
This is the current Met Office run for the ten sites. Note the spread — about 7°C between the coldest and warmest of them over the period, which is a reminder that "the weather in Britain" is never one thing.
This is a forecast for ten places, not a national picture
Every figure below is a Met Office forecast, not a measurement of what the weather did. It covers ten named sites chosen to span Great Britain, and we do not average them into a national temperature or fill in the gaps between them — ten points are a sample of populated places, not a weather map. It is here to explain why electricity demand, wind output and solar output move, not as a forecast to plan your day around.
What the next 49 hours look like
Model run 2026-11-03T21:00:00.000Z
Across the 10 sites, from Tue 3 Nov, 21:00 to Thu 5 Nov, 22:00.
- Coldest of the ten sites
- 5.4°C
- Cold raises heating demand
- Warmest of the ten sites
- 12.1°C
- Heat raises cooling demand
- Strongest wind of the ten
- 15 mph
- Measured 10m above ground, not at turbine height
- Highest UV index
- 1
- A rough proxy for solar output
Cold and damp enough for a heat pump to be defrosting
34 of the 490 site-hours in this forecast are at or below 7.0°C and at or above 80% humidity, across 3 of the 10 sites.
Frost forms on an air source heat pump's outdoor coil in cold, damp air, and the pump spends energy melting it off instead of heating the house. The 7 degrees and 80% used here are a general rule of thumb rather than a Met Office measure or a manufacturer's specification, and a well-sized pump in these conditions may barely notice. It is a count of hours in a band, not a prediction about any particular home.
This counts the 49 hours of the current forecast at ten sites. It is not a count of the defrosting a winter contains, and it is not a measurement of anything — the whole feed is a forecast.
Site by site
The range each site is forecast to see over the whole period. Wind is given in miles per hour, converted from the metres per second the Met Office publishes.
| Site | Lowest temperature | Highest temperature | Strongest wind | Strongest gust |
|---|---|---|---|---|
| AberdeenScotland | 7.6°C | 10.6°C | 9 mph | 14 mph |
| AberystwythWales | 5.9°C | 11.6°C | 11 mph | 20 mph |
| BirminghamEngland | 6.0°C | 10.4°C | 12 mph | 25 mph |
| CardiffWales | 8.0°C | 10.7°C | 15 mph | 28 mph |
| GlasgowScotland | 5.4°C | 10.4°C | 10 mph | 19 mph |
| LondonEngland | 8.8°C | 10.7°C | 13 mph | 28 mph |
| ManchesterEngland | 7.9°C | 12.1°C | 11 mph | 22 mph |
| Newcastle upon TyneEngland | 7.4°C | 10.9°C | 13 mph | 24 mph |
| NorwichEngland | 8.1°C | 11.2°C | 13 mph | 25 mph |
| PlymouthEngland | 8.5°C | 10.6°C | 14 mph | 26 mph |
How to read this alongside the electricity data
- Temperature is the strongest single driver of electricity and gas demand in Great Britain. A cold, still day is the combination that stretches the system: high heating demand and low wind output at the same time.
- The wind figures are 10 metres above ground at a city site. Wind farms sit far higher, usually offshore, and see very different speeds. Treat these as direction of travel, not as turbine input.
- UV index is a rough stand-in for how much sun solar panels are getting. It is not irradiance and it is not a solar output forecast.
- All of it is a forecast. It will be wrong to some degree, and it is never a record of what happened.
Source
Met Office — Weather DataHub — Global Spot hourly site-specific forecast. Model run 2026-11-03T21:00:00.000Z · retrieved Tue 3 Nov, 22:19.
Contains Met Office data
Cold and still: the expensive combination
Cold, still weather combines high heating demand with low wind output. Gas generation often fills the gap and can raise wholesale prices. Milder or windier weather usually eases both pressures.
How to read wind and sunshine
Wind readings are taken ten metres above ground at city sites. They show the wider weather pattern, not the wind speed at turbine height or offshore.
UV index is a broad indication of sunshine, not a solar generation forecast. Current solar output is shown on the live electricity page.
What this means for your bill
Weather changes how much energy a home uses. Whether it also changes the unit price depends on the tariff.
- Standard variable tariff: the price cap sets your unit rate for a quarter. A cold spell raises use, not the current unit rate.
- Fixed tariff: the unit rate stays fixed, but cold weather can increase consumption.
- Tracker or agile tariff: wholesale movements can reach you within a day or half hour. See the Octopus Tracker and Octopus Agile tariffs for the practical differences.
Heat-pump performance also changes with outside temperature. See air source heat pumps and typical household energy use for more detail.
Frequently asked questions
Does cold weather make my energy bill go up?
Directly, yes — a colder home loses heat faster, so your heating runs longer to hold the same temperature. Indirectly it can too: cold, still weather across the country raises national demand while wind output is low, which pushes up wholesale prices. On a standard variable tariff you would not see that for months, if at all, because the price cap smooths it. On a tracker or agile tariff you can see it within a day.
Why does wind matter for electricity prices?
Wind farms have almost no fuel cost, so when the wind blows hard they push more expensive gas generation out of the market and wholesale prices fall. When wind output collapses, gas plants set the price instead — and gas is the most expensive thing usually running. That is why a still winter day costs more than a blustery one.
Is this a weather forecast I can plan my day around?
No. It covers ten locations and is here to help explain energy demand and renewable output. Use the Met Office for a local forecast.
Why is the wind speed lower than I would expect?
These readings are ten metres above ground at city sites. Wind turbines sit far higher, usually offshore, where wind is stronger and steadier. Treat the figures here as direction of travel for the weather system, not as what the wind fleet is seeing.
Can I use the UV index to predict solar output?
Only loosely. UV index is a rough proxy for how much sun is reaching the ground, but it is not irradiance and it is not a solar generation forecast. It is useful for telling a bright day from a dull one, and not much more.
