Is it safe to switch electric radiators on and off repeatedly?

Yes. Resistive heaters have no moving parts and are designed for hundreds of thousands of switching cycles. There is no mechanical wear, no startup surge worth worrying about, and no degradation from frequent on/off cycling. This is the same principle behind every thermostat that has ever existed.

Will my room get uncomfortably cold during the off hours?

It depends on the room's insulation and thermal mass. Most modern, reasonably insulated rooms retain heat for 1–3 hours after the heater turns off. Elewatt schedules heating during the cheapest hours — often late night and early morning — so the room stays warm through the day. You can also adjust how many hours per day the heater runs.

How much can I realistically save on heating?

Typically 20–40% of your heating electricity cost, depending on your contract type and usage. The table above shows what that means in your country for typical room sizes. The calculator on this page gives you a personalised estimate.

Which electric heaters are compatible with Elewatt?

Any plug-in electric heater up to 2.5 kW (12 A) works directly with a Shelly Plug S Gen3 — no wiring required. For hardwired heaters or panels up to 5.5 kW, a Shelly Plus 1PM (requires an electrician) is recommended. Oil-filled radiators, panel heaters, fan heaters, and infrared panels all work the same way.

Can I still control my heater manually?

Yes. The Shelly Smart Control app lets you turn the device on or off instantly, or set a manual override for a fixed duration. The physical button on the Shelly Plug also works. Elewatt pushes a fresh schedule each day, so the next day automation resumes automatically.

What if the electricity price is cheap all day?

Elewatt picks the cheapest N hours you specify (e.g. 8 h). If prices are uniformly low, it simply chooses the overall cheapest window. You always pay the lowest possible rate for the amount of heating time you need.

Smart Heating · Cut Energy Costs

Electric Radiators & Smart Heating: Cut your winter electricity bill

Space heating is the biggest energy use in European homes — 62.5% of household energy in 2023, according to Eurostat. Electric radiators are 100% efficient — meaning the biggest lever for savings isn't the device itself, but when it runs. Automating your radiators to heat during the cheapest hours can cut your heating bill by 30–40% without any change in comfort.

Reedik Lindau

Published 5 March 2026 · Updated 6 October 2026

Get started free Connect Shelly

Couple drinking coffee in a warm home on a snowy winter day — Source: Yan Krukau / Pexels

Why smart heating makes sense

Electric radiators are the simplest heating system to automate: they're resistive loads that turn on and off instantly, with no warm-up cycles needed. A typical home needs 6–10 hours of heating per winter day — and with thermal mass in walls and furniture, heating for 4 hours during cheap overnight prices keeps the room warm for several hours more.

Space heating's share of home energy

~63%

EU households, 2023 (Eurostat)

Efficiency of electric radiators

100%

all electricity becomes heat

Potential savings

30–40%

on heating costs with smart scheduling

Choosing the right device

The right Shelly device depends on the radiator's rated power. Check the nameplate on your radiator.

Load	Current	Device	Notes
Single radiator ≤2.5 kW	≤12 A	Shelly Plug S Gen3	Plug & play
Radiator 2.5–5.5 kW	≤25 A	Shelly Plus 1PM	Requires wiring
Large / 3-phase systems	>25 A	Shelly Pro 3	⚠️ Professional install recommended

Single radiator ≤2.5 kW

Current: ≤12 A
Device: Shelly Plug S Gen3
Notes: Plug & play

Radiator 2.5–5.5 kW

Current: ≤25 A
Device: Shelly Plus 1PM
Notes: Requires wiring

Large / 3-phase systems

Current: >25 A
Device: Shelly Pro 3
Notes: ⚠️ Professional install recommended

Mains wiring — safety note

Shelly Plus 1PM and Shelly Pro 3 involve mains (230 V / 400 V) wiring and should be installed by a licensed electrician. Experienced DIY enthusiasts can manage it with the detailed official documentation, but when in doubt, hire a professional. Always isolate the circuit before working on it.

How Elewatt automates your heating

1Install a Shelly device (Plug S Gen3 for ≤2.5 kW, Plus 1PM for larger) on your radiator circuit.
2In Elewatt, create a duration filter: e.g. "6 hours between 22:00–08:00".
3Link the filter to your Shelly device. Each evening, Elewatt picks the cheapest 6-hour window from tomorrow's prices and pushes the schedule.
4Your radiator heats the room during the cheapest night hours, and the thermal mass keeps it warm through the morning peak.

Create a filter About Shelly Plug S Gen3

Estimated savings by room size (winter)

180 heating days. “Without Elewatt” runs the radiator in the day's most expensive hours, “with Elewatt” in the cheapest.

Room	Power	Runtime	Annual kWh	Without Elewatt	With Elewatt	Savings
Small (12 m²)	1.0 kW	6 h/day	1,080 kWh	…	…	…
Medium (20 m²)	1.5 kW	8 h/day	2,160 kWh	…	…	…
Large (30 m²)	2.5 kW	8 h/day	3,600 kWh	…	…	…

Small (12 m²)

Power: 1.0 kW
Runtime: 6 h/day
Annual kWh: 1,080 kWh
Without Elewatt: …
With Elewatt: …
Savings: …

Medium (20 m²)

Power: 1.5 kW
Runtime: 8 h/day
Annual kWh: 2,160 kWh
Without Elewatt: …
With Elewatt: …
Savings: …

Large (30 m²)

Power: 2.5 kW
Runtime: 8 h/day
Annual kWh: 3,600 kWh
Without Elewatt: …
With Elewatt: …
Savings: …

Calculate your savings

Adjust the sliders to match your radiator's power and daily runtime.

Savings Calculator

Estimate how much you could save by running your device during the cheapest hours.

Device power1.5 kW

0.1 kW22 kW

Hours per day8 h/day

1 h24 h

Days per year365 days

30 days365 days

Spot price + grid fees + taxes, Estonia · c/kWh (12-month avg)

0:00 · 14.0c

1:00 · 13.9c

2:00 · 13.0c

3:00 · 12.6c

4:00 · 12.5c

5:00 · 13.1c

6:00 · 16.1c

7:00 · 22.2c

8:00 · 24.5c

9:00 · 26.3c

10:00 · 24.0c

11:00 · 22.5c

12:00 · 18.3c

13:00 · 18.2c

14:00 · 18.2c

15:00 · 18.6c

16:00 · 23.0c

17:00 · 24.6c

18:00 · 27.2c

19:00 · 29.2c

20:00 · 26.3c

21:00 · 24.6c

22:00 · 18.6c

23:00 · 16.2c

Cheapest 8hMost expensive 8h

Daily usage

12.0 kWh/day

Annual usage

4380 kWh/year

Without Elewatt

25.9 c/kWh avg

1133 €

per year

With Elewatt

13.9 c/kWh avg

610 €

per year

Your savings

Monthly

44 €

Yearly

522 €

Shelly Plug S Gen3 (24 €) pays back in
0.5 months

Estonia: spot prices over the last 12 months + grid fees (Elektrilevi) + taxes and VAT. "Without Elewatt" assumes running during the most expensive hours. Actual savings vary by grid package and season.

Ready to cut your heating bill?

Create a free Elewatt account, connect your Shelly device and let automation handle the rest — warm rooms, lower bills.

Create Free Account Features

AI-assisted, human-reviewed — an editor checks every article before publication. Read our editorial policy

Electric Radiators & Smart Heating: Cut your winter electricity bill

Why smart heating makes sense

Choosing the right device

Mains wiring — safety note

How Elewatt automates your heating

Estimated savings by room size (winter)

Calculate your savings

Savings Calculator

Ready to cut your heating bill?

Frequently Asked Questions

Other guides

Housing co-op electricity: cut common costs

Energy management for small businesses, no BMS

Rental property electricity: real-time monitoring