Most European households can buy electricity at two or more different prices depending on the hour. The gap is often large — two to three times the price at peak compared with the cheapest window — and heating is the biggest load you can move into it. That makes time-of-use tariffs one of the few ways to cut a heating bill without lowering comfort.
The tariff shapes you will meet
- United Kingdom: Economy 7 and Economy 10 give a fixed overnight window; smart time-of-use tariffs add an evening peak price.
- France: Heures Creuses / Heures Pleines, plus Tempo days with very high peak prices on red days.
- Spain and Portugal: a valley / flat / peak structure inside the standard tariff.
- Germany, Netherlands, Nordics: dynamic contracts that follow hourly wholesale prices, sometimes going negative during windy nights.
- Italy and others: two-band tariffs with a night and weekend band.
The details differ, but the principle is identical: heating is worth running when electricity is cheap, and worth pausing when it is expensive.
Why heating is the load worth shifting
Lighting and appliances are small and mostly not flexible. Heating is large and, in the right kind of system, can be shifted without anyone noticing. The key is thermal mass: if the heat is stored in a concrete screed, a water cylinder, or a heavy storage heater, it can be released hours after it was produced.
How well different heaters shift load
- Electric underfloor heating in a screed: excellent — hours of stored heat.
- Storage heaters: designed for exactly this, though comfort control is coarse.
- Hot water cylinders with an immersion: good — heat during the cheap window and store.
- Air-to-air and panel heaters: limited, because they heat air that cools quickly.
- Heat pumps: possible, but see the efficiency caveat below.
A practical schedule pattern
On a tariff with a cheap overnight window and an expensive evening peak, a pattern that works well is:
- 23:00–06:00 (cheap): raise the setpoint two or three degrees so the floor or storage mass charges.
- 06:00–08:00 (cheap or mid): normal comfort temperature for the morning routine.
- 08:00–16:00 (mid or cheap): eco setpoint, or a second charge if your tariff has a daytime valley.
- 17:00–20:00 (peak): drop the setpoint by a degree or two and let the stored heat carry the room.
- 20:00–23:00 (mid): comfort again if needed, then prepare for the next charge.
Two or three degrees of pre-charge is usually enough. Ten degrees of pre-charge buys you nothing except a higher bill, because the building loses heat faster the warmer it gets.
Building it with a Tuya thermostat
- Separate schedules per window. A Tuya weekly schedule can hold the charge, comfort, eco, and peak blocks without manual intervention.
- Different weekday and weekend patterns, so the flat is not charged before an empty day.
- Hot water and drying scenes shifted into the cheap window where a Tuya switch or plug controls the load.
- Zone temperature limits with radiator valves so bedrooms stay cooler during the charge.
- Holiday mode that stops the charging pattern entirely while you are away.
On dynamic hourly tariffs, the thermostat itself does not know the price, so most people use a fixed approximation of the usual cheap hours and adjust on the days that matter — or integrate the price signal separately. Even an approximation captures most of the benefit, because the cheap window is broadly predictable.
Watch-outs
- Heat pumps and night hours. Cheap electricity at 3 a.m. coincides with the coldest outdoor temperatures, and a lower outdoor temperature reduces the coefficient of performance. Sometimes running the heat pump during a milder, more expensive hour produces heat more cheaply overall. Compare cost per kilowatt-hour of heat, not per kilowatt-hour of electricity.
- Badly insulated buildings lose the stored heat. Load shifting works far better after draught-proofing and loft insulation.
- Comfort still matters. A schedule that leaves the house cold at 7 p.m. will be overridden by hand every day, and manual overrides are what destroy savings.
- Check your actual windows. The cheap period on your contract may not be the one you remember; confirm it on the bill before writing the schedule.
Getting started
- Write down your tariff windows and prices.
- Decide which loads can be shifted: underfloor zones, water heating, storage heaters, laundry.
- Set the Tuya schedule to charge during the cheapest window and reduce demand at peak.
- Check a week of meter readings against the previous week, using heating-degree days to keep the comparison fair.
- Adjust once, then leave it alone — a stable schedule beats constant fiddling.
For background on why this matters this winter, see how rising European energy prices affect heating bills. Detailed schedule templates are in the Tuya thermostat setup guide, the comparison with mechanical controls is in this article, and device options are listed in the Tuya smart home product collection.