The Global Centre for Risk and Innovation (GCRI)
Heat waves raise electricity demand for cooling at the same time as they lower what the system can supply: lines carry less, thermal plants lose efficiency and cooling water, and solar panels produce less per unit of sunlight. Cold spells do the same to heating demand and gas supply. This page sets out how temperature extremes stress energy systems, how cooling access shapes health risk, and what evidence operators, health agencies and planners use.
GCRI · Established · service level R0
Grid stress in a heat wave is the squeeze on a power system from both sides: cooling demand rises while lines carry less, thermal plants lose efficiency and cooling water, and solar panels produce less per unit of sunlight. Cold spells do the same through heating and gas demand. Access to cooling is also a health protection, so outages during heat raise health risk.
Coastal exposure, deserts, deltas and glaciers across the region, shown for Canada as an example geography for this subject.
Cooling requirements and extreme heat. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.
Cooling demand climbs steeply above a comfort threshold, and electric heating does the same in cold spells. Summer peaks arrive in the late afternoon and evening, when solar output is already falling and the grid leans on other resources.
Overhead lines sag and must be derated, transformers overheat, and thermal plants lose output or are curtailed when river water exceeds discharge temperature limits. In cold extremes, gas wells, pipelines and plant equipment can freeze.
A heat dome raises demand across a whole region and its neighbours at once, so imports are scarce exactly when they are needed. Wildfire risk in the same days may force operators to de-energise lines preventively.
Where air conditioning is the main protection against heat illness, an outage during a heat wave becomes a public health emergency. Older people, those living alone and households without cooling carry most of the risk.
Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.
| Term | Definition |
|---|---|
| Cooling degree days | The sum over days of how far mean temperature exceeds a base temperature, a proxy for cooling energy demand. |
| Line derating | Reducing the current a power line may carry because high air temperature and low wind limit how much heat it can shed. |
| Universal thermal climate index | A measure of how hot or cold conditions feel to the human body, combining temperature, humidity, wind and radiation. |
Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.
| Indicator | Unit | Cadence | Source type | Label |
|---|---|---|---|---|
| Cooling and heating degree days | degree days | daily and annual | Reanalysis and station temperature | OBSERVED |
| Peak demand sensitivity to temperature | megawatts per degree Celsius | seasonal | Operator load records and weather | ESTIMATED |
| Overhead line derating | percent of nominal rating | hourly | Operator dynamic line rating | MODELLED |
| Thermal plant curtailment for cooling water | megawatts; hours | per event | Plant and operator notifications | REPORTED |
| Household access to cooling | percent of households | periodic survey | Household surveys | ESTIMATED |
| Universal thermal climate index | degrees Celsius | hourly | Reanalysis-derived heat stress | MODELLED |
| Heat-related emergency admissions during outages | admissions | per event | Health surveillance linked to outage records | REPORTED |
The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.
Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.
Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.
| Source | What it gives | Licence class |
|---|---|---|
| ERA5 and ERA5-HEAT (Copernicus) | Hourly temperature and thermal comfort indices worldwide | Free and open, attribution |
| Eurostat cooling and heating degree days | Degree days by country and region | Free reuse, attribution |
| ENTSO-E and EIA hourly demand data | Load records to estimate temperature sensitivity | ENTSO-E terms; public domain |
| ENTSO-E unavailability of generation units | Notified outages and derating of thermal plants | Free, registration, ENTSO-E terms |
| IEA cooling and buildings data | Air-conditioner stocks and cooling energy use by region | IEA terms |
| National heat-health warning systems and surveillance | Heat alerts, excess mortality and hospital admissions | Public records, terms per agency |
Energy Nexus prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.
| Who decides | The question | Evidence this page serves |
|---|---|---|
| Transmission system operators | How much reserve to hold ahead of a forecast heat wave or cold spell | Temperature-demand curves, derating estimates, neighbouring systems' expected peaks |
| Public health agencies | Which neighbourhoods and facilities need priority protection from heat during an outage | Cooling dependence maps, outage exposure, heat-stress forecasts |
| Environmental regulators | Whether and when to grant temporary derogations from cooling-water temperature limits | River temperature records, plant curtailment, ecological evidence |
| Building and planning authorities | How cooling standards and passive design reduce peak demand | Demand response curves and building stock data |
On the demand side, cooling load rises steeply with temperature, especially when nights stay hot and buildings cannot shed heat. On the supply side, conductors sag and must carry less current when hot, transformers age faster, and thermal and nuclear plants lose efficiency or must reduce output when cooling water is too warm or environmental limits on discharge temperature are reached. Solar panels also produce less per unit of sunlight when hot.
Heat often coincides with drought, low wind and wildfire risk, which can force preventive shutdowns of lines. The result is a common-cause stress that standard planning, which assumes independent failures, may underestimate. In cold climates, electrified heating creates the mirror image: very high demand during cold, still periods.
Statistical and building-physics models link weather to load, using forecasting and time-series methods. They are less reliable beyond the range of observed temperatures.
Engineering standards describe how capacity falls with temperature. Actual behaviour depends on equipment age and local conditions.
Downscaled climate model outputs describe future heat. They carry model and scenario uncertainty that must be carried into energy results.
Epidemiological evidence links heat and power loss to health harm. Data on outage exposure by household is often limited.
The current service level is R0: information and enquiries. An enquiry receives a reference and names the next step; applications, payments, compute allocations and registrations open only when their team, terms and review capacity exist.