Electric heating and Tempo: how much red days weigh
Red days fall in hard frost, when heating runs hardest: here is the share of your heating they concentrate, as measured by RTE.
Tempo red days do not fall at random: RTE places them when national net demand peaks, which means in hard frost, when radiators and heat pumps run hardest. To measure this effect we combined day-by-day national demand published by RTE with the colour of every day since 2014. Averaged over 12 seasons, the 22 red days concentrated 19.4 % of heating consumption, the 43 white days 29.4 % and blue days 51.2 %. An electrically heated home therefore uses about a fifth of its annual heating on the days when a kilowatt-hour costs €0.7295 between 06:00 and 22:00. That is the first figure to know before choosing Tempo, and the most powerful lever to cut the bill: every degree turned down on those days counts. The mini-calculator puts a cost on it from your own heating consumption.
Your heating on red days
Red-day heating, with your cut
€521
| Heating share falling on red days | 19.4 % |
| kWh heated on red days | 933 kWh |
| With no cut at all | €652 |
| The same kWh on the Off-peak option | €184 |
Heating profile: national demand measured by RTE, 30% at night, prices incl. tax from 1 August 2026.
Checked by Radif Partners · Editorial policy · Method and sources
What the heating profile measures
RTE publishes in éCO2mix the electricity consumption of the whole of France, half-hour by half-hour, going back more than ten years. For each Tempo season we took each day’s average, then removed the summer baseline, the median consumption from May to September when almost nobody heats. Whatever exceeds the baseline depends on the cold: that is the temperature-sensitive part, the heating. It then only remains to add that part up over the season’s blue, white and red days.
Each day is counted as a Tempo day, 06:00 to 06:00 the next morning, from the quarter-hour readings. The measure uses national demand, whereas RTE’s method picks red days on net demand, after wind and solar output: both climb together with the cold, which keeps the split true to the essentials.
Season by season
| Season | Red days | Heating on red days | On white days | On blue days |
|---|---|---|---|---|
| 2014-2015 | 22 | 20.7 % | 30.3 % | 49.0 % |
| 2015-2016 | 22 | 19.3 % | 30.2 % | 50.5 % |
| 2016-2017 | 22 | 18.7 % | 30.1 % | 51.2 % |
| 2017-2018 | 22 | 18.8 % | 30.7 % | 50.5 % |
| 2018-2019 | 22 | 19.4 % | 29.0 % | 51.6 % |
| 2019-2020 | 18 | 15.5 % | 29.9 % | 54.6 % |
| 2020-2021 | 22 | 20.6 % | 28.2 % | 51.2 % |
| 2021-2022 | 22 | 19.9 % | 27.4 % | 52.7 % |
| 2022-2023 | 22 | 23.8 % | 29.4 % | 46.8 % |
| 2023-2024 | 22 | 21.0 % | 28.6 % | 50.4 % |
| 2024-2025 | 22 | 20.1 % | 31.4 % | 48.6 % |
| 2025-2026 | 22 | 15.5 % | 28.0 % | 56.6 % |
The red-day share ranges from 15.5 % (2025-2026) to 23.8 % (2022-2023). The differences follow the weather: a winter whose cold is packed into a few weeks loads its red days more heavily, a mild winter spreads heating over blue days. The 2019-2020 season, cut to 18 red days by the regulator, naturally shows a lower share.
What red-day heating costs
Applied to a few annual heating consumptions, with 30% of the heat produced at night, the average gives:
| Heating a year | Of which red days | Tempo cost of red days | With a 20% cut | Same kWh on Off-peak |
|---|---|---|---|---|
| 4,000 kWh | 777 kWh | €435 | €348 | €154 |
| 6,000 kWh | 1,166 kWh | €652 | €521 | €230 |
| 10,000 kWh | 1,943 kWh | €1,086 | €869 | €384 |
The gap between the Tempo column and the Off-peak column is the price of red days. It has to be made up by blue and white days, cheaper on Tempo, for the option to pay. The guide is Tempo worth it works out the break-even point, and the comparison tool applies it to your whole consumption.
Radiators, heat pumps, storage
Electric radiators turn each kWh into heat and nothing more: their consumption tracks the cold closely, and red days take a share close to the national average. A heat pump produces more heat than the electricity it uses, which cuts every kWh, red ones included; but its efficiency falls in severe cold, so its red days weigh a little more than its other days. Systems that store heat, underfloor heating, storage heaters, buffer tanks, can charge at night at off-peak prices and release the heat during the day: they get the most out of Tempo.
Schedule rather than suffer
A programmable thermostat, or a controller that receives the Tempo signal from the Linky meter, applies the set-back without you thinking about it: lower setting from 06:00 to 22:00 on red days, normal afterwards. Since the Tempo day starts at 06:00, warming the house between 04:00 and 06:00 is paid at the previous day’s off-peak price. For safety, always keep a sensible minimum in every room, especially where young children, elderly or ill people live.
A season’s 22 red days are published one by one, the day before, on RTE’s calendar. To see where the season stands and how many are left, see the season history and the guide on what to do on a red day.
What white days mean for heating
Red days get the attention, but the 43 white days carry more heating: 29.4 % on average, against 19.4 % for red days. Their peak price, €0.1921, stays close to the other options, though. Over a year of 6,000 kWh of heating, with 30% at night, the split gives:
| Colour | Heating share | kWh | Cost on Tempo | Same kWh on Off-peak |
|---|---|---|---|---|
| Blue | 51.2 % | 3,069 kWh | €480 | €606 |
| White | 29.4 % | 1,765 kWh | €319 | €349 |
| Red | 19.4 % | 1,166 kWh | €652 | €230 |
Blue days save money, white days a little, red days lose it. That red line is the one to shrink if electric heating is to stay a winner on Tempo.
Reading your own split
The national average is a starting point. A household already on Tempo knows its real split: the bill or online account gives the kWh for each colour at peak and off-peak. Dividing red kWh by the total gives your own share. If it is well above the average, your home is more sensitive to cold than most, which argues for insulation or a firmer set-back on red days; if it is lower, Tempo suits you all the better. The Tempo prices page recalculates a whole year from those readings.
A word on wood and gas back-up
Some households switch to a wood stove or a back-up boiler on red days. This site’s calculation covers electricity only: it knows neither the price of your wood nor that of your gas. A properly installed back-up can sharply cut red kWh; a portable fuel-burning heater in a closed room, on the other hand, carries a real risk of poisoning and has no place in an occupied home.
Insulate before you choose
The faster a home loses heat, the more closely its heating follows the cold, and the more red days weigh. Insulation therefore works twice on a Tempo bill: it cuts heating kilowatt-hours all year round, and it lets you lower the setting on red days without the house cooling down. A well-insulated house holds the heat stored overnight for several hours, while a poorly insulated one loses it in tens of minutes.
Before judging Tempo on a single season, look at what has changed at home too: a new heating system, building work, one more person at home during the day. They often explain a bill rising from one winter to the next better than the tariff does.
English speakers settling in France will meet the energy performance certificate, the DPE, when renting or buying: a home rated poorly for energy is one where heating, and therefore red days, will weigh more.
For an English speaker used to gas central heating, French all-electric homes can come as a surprise: radiators in every room, a water heater in a cupboard, and a bill that climbs steeply in January. Tempo turns that seasonality into a choice: pay a premium on a few cold days, or adjust and pay less across the year.